1
|
Lee J, Shin DJ, Jo U, Lee JY. Reverse Intersystem Crossing Boosting Sensitizer for Ultra-High Efficiency Blue Organic Light-Emitting Diode. ACS APPLIED MATERIALS & INTERFACES 2024; 16:43786-43794. [PMID: 39107103 DOI: 10.1021/acsami.4c09057] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/09/2024]
Abstract
In designing thermally activated delayed fluorescence (TADF) emitters, a high reverse intersystem crossing (RISC) rate with a high photoluminescence quantum yield is essential. Herein, two blue TADF molecules, 2',5'-di(9H-carbazol-9-yl)-3',6'-bis(3,6-ditert-butyl-9H-carbazol-9-yl)-[1,1':4',1″-terphenyl]-4,4″-dicarbonitrile (CzTCzPhBN) and 2',5'-bis(3,6-ditert-butyl-9H-carbazol-9-yl)-3',6'-bis(3,6-diphenyl-9H-carbazol-9-yl)-[1,1':4',1″-terphenyl]-4,4″-dicarbonitrile (PhCzTCzPhBN) with a high RISC rate, were developed through donor engineering. CzTCzPhBN and PhCzTCzPhBN showed a high RISC rate of 4.00 × 105 and 16.62 × 105 s-1, respectively, with a high photoluminescence quantum yield of 80.1 and 84.9%, which resulted in high external quantum efficiency of 27.0 and 27.8% with color coordinates (0.148, 0.170) and (0.150, 0.230) in blue TADF organic light-emitting diodes, respectively. The high RISC rate and device efficiency inspired two TADF molecules to be used as sensitizers in hyperfluorescence devices. The hyperfluorescence devices showed ultra-high external quantum efficiency of 30.7 and 36.4% with color coordinates (0.125, 0.164) and (0.127, 0.193), respectively.
Collapse
Affiliation(s)
- Jihyun Lee
- School of Chemical Engineering, Sungkyunkwan University, 2066, Seobu-ro, Jangan-gu, Suwon-si, Gyeonggi-do 16419, Republic of Korea
| | - Dong Jin Shin
- School of Chemical Engineering, Sungkyunkwan University, 2066, Seobu-ro, Jangan-gu, Suwon-si, Gyeonggi-do 16419, Republic of Korea
| | - Unhyeok Jo
- School of Chemical Engineering, Sungkyunkwan University, 2066, Seobu-ro, Jangan-gu, Suwon-si, Gyeonggi-do 16419, Republic of Korea
| | - Jun Yeob Lee
- School of Chemical Engineering, Sungkyunkwan University, 2066, Seobu-ro, Jangan-gu, Suwon-si, Gyeonggi-do 16419, Republic of Korea
- SKKU Institute of Energy Science and Technology, Sungkyunkwan University, 2066, Seobu-ro, Jangan-gu, Suwon, Gyeonggi 16419, Republic of Korea
| |
Collapse
|
2
|
Di Maiolo F, Phan Huu DKA, Giavazzi D, Landi A, Racchi O, Painelli A. Shedding light on thermally-activated delayed fluorescence. Chem Sci 2024; 15:5434-5450. [PMID: 38638233 PMCID: PMC11023041 DOI: 10.1039/d4sc00033a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2024] [Accepted: 02/17/2024] [Indexed: 04/20/2024] Open
Abstract
Thermally activated delayed fluorescence (TADF) is a hot research topic in view of its impressive applications in a wide variety of fields from organic LEDs to photodynamic therapy and metal-free photocatalysis. TADF is a rare and fragile phenomenon that requires a delicate equilibrium between tiny singlet-triplet gaps, sizable spin-orbit couplings, conformational flexibility and a balanced contribution of charge transfer and local excited states. To make the picture more complex, this precarious equilibrium is non-trivially affected by the interaction of the TADF dye with its local environment. The concurrent optimization of the dye and of the embedding medium is therefore of paramount importance to boost practical applications of TADF. Towards this aim, refined theoretical and computational approaches must be cleverly exploited, paying attention to the reliability of adopted approximations. In this perspective, we will address some of the most important issues in the field. Specifically, we will critically review theoretical and computational approaches to TADF rates, highlighting the limits of widespread approaches. Environmental effects on the TADF photophysics are discussed in detail, focusing on the major role played by dielectric and conformational disorder in liquid solutions and amorphous matrices.
Collapse
Affiliation(s)
- Francesco Di Maiolo
- Dept. Chemistry, Life Science and Environmental Sustainability, University of Parma Parco Area delle Scienze 17/A 43124 Parma Italy
| | - D K Andrea Phan Huu
- Dept. Chemistry, Life Science and Environmental Sustainability, University of Parma Parco Area delle Scienze 17/A 43124 Parma Italy
| | - Davide Giavazzi
- Dept. Chemistry, Life Science and Environmental Sustainability, University of Parma Parco Area delle Scienze 17/A 43124 Parma Italy
| | - Andrea Landi
- Dept. Chemistry, Life Science and Environmental Sustainability, University of Parma Parco Area delle Scienze 17/A 43124 Parma Italy
| | - Ottavia Racchi
- Dept. Chemistry, Life Science and Environmental Sustainability, University of Parma Parco Area delle Scienze 17/A 43124 Parma Italy
| | - Anna Painelli
- Dept. Chemistry, Life Science and Environmental Sustainability, University of Parma Parco Area delle Scienze 17/A 43124 Parma Italy
| |
Collapse
|
3
|
Bergmann K, Hudson ZM. Excited-state dynamics of C 3-symmetric heptazine-based thermally activated delayed-fluorescence emitters. Faraday Discuss 2024; 250:181-191. [PMID: 37975289 DOI: 10.1039/d3fd00121k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2023]
Abstract
Heptazine-based materials have recently emerged as a promising motif for thermally activated delayed fluorescence, as their near-zero or negative singlet-triplet energy gaps enable extremely fast reverse intersystem crossing (rISC) rates. Another method for achieving a high rate of rISC is through the use of highly symmetric emitters, which benefit from energy-level degeneracies and a high density of states. Here, we investigate the effect of combining these two design strategies on the excited-state dynamics of C3-symmetric emitters containing heptazine cores. We find that in two of the four emitters studied, the S1 state has a high degree of locally excited (LE) character with density on the heptazine moiety, preventing excited-state localization and a loss of symmetry in the energy-minimized S1 geometry. Surprisingly, these symmetric molecules still suffer from a loss of density of triplet states below the S1 state. Overall, we find that maintaining C3 symmetry will not necessarily maintain density of states, but that heptazine-based materials with LE S1 states still benefit from maximized rISC rates via increased spin-orbit coupling with low-lying charge-transfer triplet states and exhibit advantageous photophysical properties, such as near-unity photoluminescence quantum yields and high colour purity.
Collapse
Affiliation(s)
- Katrina Bergmann
- Department of Chemistry, The University of British Columbia, 2036 Main Mall, Vancouver, BC, Canada, V6T 1Z1.
| | - Zachary M Hudson
- Department of Chemistry, The University of British Columbia, 2036 Main Mall, Vancouver, BC, Canada, V6T 1Z1.
| |
Collapse
|
4
|
Matussek M, Kurpanik-Wójcik A, Gogoc S, Fijołek A, Filapek M, Naumczuk B, Data P. Electroactive Dyes Based on 1,8-Naphthalimide with Acetylene Linkers as Promising OLED Materials - the Relationship Between Structure and Photophysical Properties. Chemistry 2023; 29:e202302115. [PMID: 37548079 DOI: 10.1002/chem.202302115] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2023] [Revised: 08/03/2023] [Accepted: 08/04/2023] [Indexed: 08/08/2023]
Abstract
Four A-π-D-π-A type small organic molecules with 1,8-naphthalimide motifs were successfully synthesised. The designed compounds are built of two 1,8-naphthalimide units linked via ethynyl π-linkages with selected functionalised donor motifs i. e. 2,2'-bithiophene, fluorene, phenothiazine and carbazole derivative. The synthesis based on Sonogashira cross-coupling allowed us to obtain the presented dyes with good yields. The resulting symmetrical small molecules' optical, electrochemical and thermal properties were thoroughly investigated, and their potential applicability for the OLED devices was demonstrated. In addition, the relationship between molecular structure and properties was considered by employing experimental and theoretical studies. As a result of using various donor groups, it was possible to achieve efficient electroluminescence in the range from green (DEV4) to orange-red light (DEV3) with a maximum luminance of 3 820 cd/m2 for DEV4. Upon the insertion of an acetylene linker to the designed molecules, the free rotation of D and A fragments, and hence the effective π-electron communication within the entire molecule, is possible, which was confirmed by DFT studies. The obtained dyes are characterised by high thermal stability, reversible oxidation-reduction process, satisfactory optoelectronic properties and good solubility in organic solvents, which is advisable for the application in small molecular organic light-emitting diodes (SM-OLEDs) technology.
Collapse
Affiliation(s)
- Marek Matussek
- Institute of Chemistry, University of Silesia, Szkolna 9, 40-006, Katowice, Poland
| | | | - Szymon Gogoc
- Faculty of Chemistry, Silesian University of Technology, Strzody 9, 44-100, Gliwice, Poland
| | - Aleksandra Fijołek
- Institute of Chemistry, University of Silesia, Szkolna 9, 40-006, Katowice, Poland
| | - Michał Filapek
- Institute of Chemistry, University of Silesia, Szkolna 9, 40-006, Katowice, Poland
| | - Beata Naumczuk
- Institute of Organic Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224, Warsaw, Poland
| | - Przemysław Data
- Department of Molecular Physics, Lodz University of Technology, Żeromskiego 116, 90-543, Łódź, Poland
| |
Collapse
|
5
|
Siddiqui I, Kumar S, Tsai YF, Gautam P, Shahnawaz, Kesavan K, Lin JT, Khai L, Chou KH, Choudhury A, Grigalevicius S, Jou JH. Status and Challenges of Blue OLEDs: A Review. NANOMATERIALS (BASEL, SWITZERLAND) 2023; 13:2521. [PMID: 37764550 PMCID: PMC10536903 DOI: 10.3390/nano13182521] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2023] [Revised: 09/04/2023] [Accepted: 09/05/2023] [Indexed: 09/29/2023]
Abstract
Organic light-emitting diodes (OLEDs) have outperformed conventional display technologies in smartphones, smartwatches, tablets, and televisions while gradually growing to cover a sizable fraction of the solid-state lighting industry. Blue emission is a crucial chromatic component for realizing high-quality red, green, blue, and yellow (RGBY) and RGB white display technologies and solid-state lighting sources. For consumer products with desirable lifetimes and efficiency, deep blue emissions with much higher power efficiency and operation time are necessary prerequisites. This article reviews over 700 papers covering various factors, namely, the crucial role of blue emission for full-color displays and solid-state lighting, the performance status of blue OLEDs, and the systematic development of fluorescent, phosphorescent, and thermally activated delayed fluorescence blue emitters. In addition, various challenges concerning deep blue efficiency, lifetime, and approaches to realizing deeper blue emission and higher efficacy for blue OLED devices are also described.
Collapse
Affiliation(s)
- Iram Siddiqui
- Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan
| | - Sudhir Kumar
- Institute for Chemical and Bioengineering, ETH Zürich, 8093 Zürich, Switzerland
| | - Yi-Fang Tsai
- Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan
| | - Prakalp Gautam
- Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan
| | - Shahnawaz
- Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan
| | - Kiran Kesavan
- Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan
| | - Jin-Ting Lin
- Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan
| | - Luke Khai
- Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan
| | - Kuo-Hsien Chou
- Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan
| | - Abhijeet Choudhury
- Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan
| | - Saulius Grigalevicius
- Department of Polymer Chemistry and Technology, Kaunas University of Technology, LT-50254 Kaunas, Lithuania
| | - Jwo-Huei Jou
- Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan
| |
Collapse
|
6
|
Hussain A, Kanwal F, Irfan A, Hassan M, Zhang J. Exploring the Influence of Engineering the Linker between the Donor and Acceptor Fragments on Thermally Activated Delayed Fluorescence Characteristics. ACS OMEGA 2023; 8:15638-15649. [PMID: 37151492 PMCID: PMC10157659 DOI: 10.1021/acsomega.3c01098] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/18/2023] [Accepted: 04/06/2023] [Indexed: 05/09/2023]
Abstract
We have expounded the unique molecular design architecture for efficient thermally activated delayed fluorescence (TADF) materials based on a donor-linker-acceptor-linker-donor (D-L-A-L-D) framework, which can be employed as predecessors of organic light-emitting diode (OLED) devices. Different from traditional donor-acceptor-type (D-A-type) TADF scaffolds, the D-L-A-L-D structural design avoids direct coupling amid the D and A fragments allowing the highest occupied molecular orbitals (HOMOs) and the lowest unoccupied molecular orbitals (LUMOs) to be spatially separated. It results in a reduced overlap between HOMOs and LUMOs, thus realizing fairly a slight singlet-triplet energy gap (ΔE ST) and higher photoluminescence quantum yield (Φ). We revealed that manipulating a linker between D and A fragments in intramolecular charge transfer compounds is an auspicious approach for realizing small ΔE ST. Herein, we report a group of organic electroluminescent D-L-A-L-D-type molecules with different electron-donating and electron-accepting moieties using density functional theory calculations and time-dependent density functional theory calculations. Two types of linkers, the π-conjugated phenylene (-C6H4-) and aliphatic alkyl chains or σ-spacer (-CH2- and -CH2-CH2-), were exploited between D and A fragments. In principle, the conjugation in D-π-A-π-D-type molecules and hyperconjugation in D-σ-A-σ-D type molecules encourage the spatial separation of the HOMO-LUMO causing a reduction in the ΔE ST. All the designed molecules show a blue-shift in the emission wavelengths (λem) over the directly linked parent molecules except DPA-DPS-C6H4 and BTPA-DPS-C6H4 which show a red-shift. Violet-blue to green-yellow (376-566 nm) λem was observed from all of the investigated molecules. Other important properties that affect the efficiency of emission quantum yields like frontier molecular orbital analysis, natural population analysis, electron excitation analysis, exciton binding energies, ionization potentials, electronic affinities, and reorganization energies of the designed molecules were also inspected. We are confident that our work will effectively give a straightforward and distinctive approach to building incredibly effective TADF-OLEDs and a new perspective on their structural design.
Collapse
Affiliation(s)
- Aftab Hussain
- School
of Chemistry, University of the Punjab, Lahore 54590, Pakistan
- . Tel.: +923426224761
| | - Farah Kanwal
- School
of Chemistry, University of the Punjab, Lahore 54590, Pakistan
| | - Ahmad Irfan
- Department
of Chemistry, College of Science, King Khalid
University, P.O. Box 9004, Abha 61413, Saudi Arabia
| | - Mehboob Hassan
- Department
of Chemistry, University of Narowal, Narowal, Punjab 51600, Pakistan
| | - Jingping Zhang
- Faculty
of Chemistry, Northeast Normal University, Changchun 130024, China
| |
Collapse
|
7
|
Jacob JM, Jennifer G A, Varathan E, Ravva MK. Improving the TADF in Corannulene‐Based Emitters via Tuning the Strength of Donor and Acceptor Groups. ADVANCED THEORY AND SIMULATIONS 2023. [DOI: 10.1002/adts.202200850] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/18/2023]
Affiliation(s)
- Jesni M. Jacob
- Department of Chemistry SRM University‐AP Guntur Andhra Pradesh 522240 India
| | - Abigail Jennifer G
- Department of Chemistry SRM Institute of Science and Technology Kattankulathur Chennai Tamil Nadu 603203 India
| | - Elumalai Varathan
- Department of Chemistry SRM Institute of Science and Technology Kattankulathur Chennai Tamil Nadu 603203 India
| | - Mahesh Kumar Ravva
- Department of Chemistry SRM University‐AP Guntur Andhra Pradesh 522240 India
| |
Collapse
|
8
|
Jiang S, Qi F, Zhang D, Lv X, Song J, Gu J, Chen J, Meng L. Carbonyl (CO)/N-based thermally activated delayed fluorescent materials with high efficiency and fast reverse intersystem crossing rate: a theoretical design and study. NEW J CHEM 2023. [DOI: 10.1039/d3nj00423f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/03/2023]
Abstract
Two novel highly efficient organic TADF materials based on MR structures have been theoretically designed and investigated.
Collapse
|
9
|
Phan Huu DK, Saseendran S, Dhali R, Franca LG, Stavrou K, Monkman A, Painelli A. Thermally Activated Delayed Fluorescence: Polarity, Rigidity, and Disorder in Condensed Phases. J Am Chem Soc 2022; 144:15211-15222. [PMID: 35944182 PMCID: PMC9413221 DOI: 10.1021/jacs.2c05537] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2022] [Indexed: 12/27/2022]
Abstract
We present a detailed and comprehensive picture of the photophysics of thermally activated delayed fluorescence (TADF). The approach relies on a few-state model, parametrized ab initio on a prototypical TADF dye, that explicitly accounts for the nonadiabatic coupling between electrons and vibrational and conformational motion, crucial to properly address (reverse) intersystem crossing rates. The Onsager model is exploited to account for the medium polarity and polarizability, with careful consideration of the different time scales of relevant degrees of freedom. TADF photophysics is then quantitatively addressed in a coherent and exhaustive approach that accurately reproduces the complex temporal evolution of emission spectra in liquid solvents as well as in solid organic matrices. The different rigidity of the two environments is responsible for the appearance in matrices of important inhomogeneous broadening phenomena that are ascribed to the intertwined contribution from (quasi)static conformational and dielectric disorder.
Collapse
Affiliation(s)
- D. K.
Andrea Phan Huu
- Department
of Chemistry, Life Sciences and Environmental Sustainability, University of Parma, 43124 Parma, Italy
| | - Sangeeth Saseendran
- Department
of Chemistry, Life Sciences and Environmental Sustainability, University of Parma, 43124 Parma, Italy
| | - Rama Dhali
- Department
of Chemistry, Life Sciences and Environmental Sustainability, University of Parma, 43124 Parma, Italy
| | | | - Kleitos Stavrou
- Department
of Physics, Durham University, South Road, Durham DH1 3LE, U.K.
| | - Andrew Monkman
- Department
of Physics, Durham University, South Road, Durham DH1 3LE, U.K.
| | - Anna Painelli
- Department
of Chemistry, Life Sciences and Environmental Sustainability, University of Parma, 43124 Parma, Italy
| |
Collapse
|
10
|
Kelly D, Franca LG, Stavrou K, Danos A, Monkman AP. Laplace Transform Fitting as a Tool To Uncover Distributions of Reverse Intersystem Crossing Rates in TADF Systems. J Phys Chem Lett 2022; 13:6981-6986. [PMID: 35881847 PMCID: PMC9358706 DOI: 10.1021/acs.jpclett.2c01864] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2022] [Accepted: 07/18/2022] [Indexed: 05/22/2023]
Abstract
Donor-acceptor (D-A) thermally activated delayed fluorescence (TADF) molecules are exquisitely sensitive to D-A dihedral angle. Although commonly simplified to an average value, these D-A angles nonetheless exist as distributions across the individual molecules embedded in films. The presence of these angle distributions translates to distributions in the rates of reverse intersystem crossing (krISC), observed as time dependent spectral shifts and multiexponential components in the emission decay, which are difficult to directly quantify. Here we apply inverse Laplace transform fitting of delayed fluorescence to directly reveal these distributions. Rather than a single average value, the crucial krISC rate is instead extracted as a density of rates. The modes and widths of these distributions vary with temperature, host environment, and intrinsic D-A torsional rigidity of different TADF molecules. This method gives new insights and deeper understanding of TADF host-guest interactions, as well as verifies future design strategies that target D-A bond rigidity.
Collapse
|
11
|
Streater D, Duisenova K, Luo J, Kohlstedt KL, Zhang J, Huang J. Impact of π-Conjugation Length on the Excited-State Dynamics of Star-Shaped Carbazole-π-Triazine Organic Chromophores. J Phys Chem A 2022; 126:3291-3300. [PMID: 35594508 DOI: 10.1021/acs.jpca.2c00682] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Correlating star-shaped donor-bridge-acceptor (DBA) molecular structures with intramolecular charge transfer (ICT) and intersystem crossing (ISC) is essential to their application in photocatalysis, photovoltaics, and organic light-emitting diodes (OLEDs). In this work, we report a systematic photophysical study on a series of star-shaped triazine-phenylene-carbazole DBA molecules with 0, 1, and 2 bridging phenylene units (pTCT-0P, pTCT-1P, pTCT-2P). Using a combination of steady-state and time-resolved spectroscopy with time-dependent density functional theory (TDDFT), we find that the bridge length can strongly impact the structural conformation, ICT, and ISC. Global target analysis of the time-resolved spectroscopy reveals that pTCT-0P has the most favorable ISC rate of 1.96 × 10-4 ps-1, which is competitive with a singlet relaxation rate of 1.92 × 10-4 ps-1. TDDFT aligns with spectroscopic results within an order of magnitude, predicting an ISC rate of 2.1 × 10-5 ps-1 and revealing that the donor/acceptor orthogonalization concomitantly suppresses singlet exciton recombination and lowers the singlet-triplet energy gap. The new fundamental insights gained from this work will help design the next generation of star-shaped DBA-type molecules for photocatalytic and photoelectronic applications.
Collapse
Affiliation(s)
- Daniel Streater
- Department of Chemistry, Marquette University, Milwaukee, Wisconsin 53201, United States
| | - Korlan Duisenova
- Department of Chemistry, Marquette University, Milwaukee, Wisconsin 53201, United States
| | - Jian Luo
- Department of Chemistry, University of Nebraska-Lincoln, Lincoln, Nebraska 68588, United States
| | - Kevin L Kohlstedt
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
| | - Jian Zhang
- Department of Chemistry, University of Nebraska-Lincoln, Lincoln, Nebraska 68588, United States.,The Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Jier Huang
- Department of Chemistry, Marquette University, Milwaukee, Wisconsin 53201, United States
| |
Collapse
|
12
|
Syntheses, crystal structures, luminescence, Hirshfeld surface analyses and thermal properties of biphenyl carbazole derivatives. J Mol Struct 2021. [DOI: 10.1016/j.molstruc.2021.131018] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
|
13
|
Vieira AA, Farias G, Costa WC, Eccher J, Bechtold IH, Durola F, Bock H. Nematic Triphenyltriazine Triesters and the Induction of the Columnar Mesophase by Fluorine Substitution. Chemistry 2021; 27:9003-9010. [PMID: 33871125 DOI: 10.1002/chem.202005456] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2020] [Indexed: 11/06/2022]
Abstract
Whereas their para homologs are not mesogenic, the disk-shaped triphenyltriazine meta-trialkylesters obtained via trimerization of 3-cyanobenzoic alkylester, which are configurationally more flexible, exhibit a monotropic nematic mesophase. Introduction of fluorine atoms into the alkyl chains or into the phenyl moieties leads to the appearance of an enantiotropic columnar mesophase. If fluorine is introduced both in the chains and in the phenyl moieties, only a monotropic mesophase remains. Fluorination of either the alkyl chains or the aromatic core, but not both, appears thus as a simple means of inducing or stabilizing columnar self-assembly in disk-shaped systems. As the homeotropically alignable columnar mesophase can thus be made to persist at room temperature, as energies higher than 3 eV of the first excited triplet state are computed in agreement with the value reported for the parent arene, and as they are not fluorescent themselves, these compounds are of promise as aligning host matrices for blue-emitting TADF devices with improved light outcoupling. Dilution of a columnar with a nonmesogenic homolog induces the nematic state, indicating that the nanoscopic make-up of both mesophases is closely related.
Collapse
Affiliation(s)
- André A Vieira
- Instituto de Química, Universidade Federal da Bahia, 40170-115, Salvador, BA, Brazil
| | - Giliandro Farias
- Departamento de Química, Universidade Federal de Santa Catarina, 88040-900, Florianópolis, SC, Brazil
| | - Wallison C Costa
- Departamento de Física, Universidade Federal de Santa Catarina, 88040-900, Florianópolis, SC, Brazil
| | - Juliana Eccher
- Departamento de Física, Universidade Federal de Santa Catarina, 88040-900, Florianópolis, SC, Brazil
| | - Ivan H Bechtold
- Departamento de Física, Universidade Federal de Santa Catarina, 88040-900, Florianópolis, SC, Brazil
| | - Fabien Durola
- Centre de Recherche Paul Pascal, CNRS & Université de Bordeaux 115 av. Schweitzer, 33600, Pessac, France
| | - Harald Bock
- Centre de Recherche Paul Pascal, CNRS & Université de Bordeaux 115 av. Schweitzer, 33600, Pessac, France
| |
Collapse
|
14
|
Wei Q, Imbrasas P, Caldera-Cruz E, Cao L, Fei N, Thomas H, Scholz R, Lenk S, Voit B, Reineke S, Ge Z. Conjugation-Induced Thermally Activated Delayed Fluorescence: Photophysics of a Carbazole-Benzophenone Monomer-to-Tetramer Molecular Series. J Phys Chem A 2021; 125:1345-1354. [PMID: 33555196 DOI: 10.1021/acs.jpca.0c08977] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Materials exhibiting thermally activated delayed fluorescence (TADF) have been extensively explored in the last decade. These emitters have great potential of being used in organic light-emitting diodes because they allow for high quantum efficiencies by utilizing triplet states via reverse intersystem crossing. In small molecules, this is done by spatially separating the highest occupied molecular orbital from the lowest unoccupied molecular orbital, forming an intramolecular charge-transfer (iCT) state and leading to a small energy difference between lowest excited singlet and triplet states (ΔEST). However, in polymer emitters, this is harder to achieve, and typical strategies usually include adding known TADF units as sidechains onto a polymer backbone. In a previous work, we proposed an alternative way to achieve a TADF polymer by repeating a non-TADF unit, polymerizing it via electron-donating carbazole moieties. The extended conjugation on the backbone reduced the ΔEST and allowed for an efficient TADF polymer. In this work, we present a more in-depth study of the shift from a non-TADF monomer to TADF oligomers. The monomer shows non-TADF emission, and we find the delayed emission to be of triplet-triplet annihilation origin. An iCT state is formed already in the dimer, leading to a much more efficient TADF emission. This is confirmed by an almost two-fold increase of photoluminescence quantum yield, a decrease in the delayed luminescence lifetime, and the respective spectral lineshapes of the molecules.
Collapse
Affiliation(s)
- Qiang Wei
- Ningbo Institute of Materials Technology & Engineering, Chinese Academy Sciences, Ningbo 315201, P. R. China.,Center for Materials Science and Optoelectronics Engineering, University of Chinese Academy of Science, Beijing 100049, P. R. China
| | - Paulius Imbrasas
- Dresden Integrated Center for Applied Physics and Photonic Materials (IAPP) and Institute for Applied Physics, Technische Universität Dresden, 01062 Dresden, Germany
| | - Enrique Caldera-Cruz
- Leibniz-Institut für Polymerforschung Dresden e.V., Hohe Straße 6, D-01069 Dresden, Germany
| | - Liang Cao
- Ningbo Institute of Materials Technology & Engineering, Chinese Academy Sciences, Ningbo 315201, P. R. China.,Center for Materials Science and Optoelectronics Engineering, University of Chinese Academy of Science, Beijing 100049, P. R. China
| | - Nanan Fei
- Ningbo Institute of Materials Technology & Engineering, Chinese Academy Sciences, Ningbo 315201, P. R. China.,Center for Materials Science and Optoelectronics Engineering, University of Chinese Academy of Science, Beijing 100049, P. R. China
| | - Heidi Thomas
- Dresden Integrated Center for Applied Physics and Photonic Materials (IAPP) and Institute for Applied Physics, Technische Universität Dresden, 01062 Dresden, Germany
| | - Reinhard Scholz
- Dresden Integrated Center for Applied Physics and Photonic Materials (IAPP) and Institute for Applied Physics, Technische Universität Dresden, 01062 Dresden, Germany.,Leibniz-Institut für Polymerforschung Dresden e.V., Hohe Straße 6, D-01069 Dresden, Germany
| | - Simone Lenk
- Dresden Integrated Center for Applied Physics and Photonic Materials (IAPP) and Institute for Applied Physics, Technische Universität Dresden, 01062 Dresden, Germany
| | - Brigitte Voit
- Leibniz-Institut für Polymerforschung Dresden e.V., Hohe Straße 6, D-01069 Dresden, Germany.,Organic Chemistry of Polymers, Technische Universität Dresden, 01062 Dresden, Germany
| | - Sebastian Reineke
- Dresden Integrated Center for Applied Physics and Photonic Materials (IAPP) and Institute for Applied Physics, Technische Universität Dresden, 01062 Dresden, Germany
| | - Ziyi Ge
- Ningbo Institute of Materials Technology & Engineering, Chinese Academy Sciences, Ningbo 315201, P. R. China.,Center for Materials Science and Optoelectronics Engineering, University of Chinese Academy of Science, Beijing 100049, P. R. China
| |
Collapse
|
15
|
Chen D, Zysman-Colman E. Exploring the possibility of using fluorine-involved non-conjugated electron-withdrawing groups for thermally activated delayed fluorescence emitters by TD-DFT calculation. Beilstein J Org Chem 2021; 17:210-223. [PMID: 33564331 PMCID: PMC7849250 DOI: 10.3762/bjoc.17.21] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2020] [Accepted: 01/05/2021] [Indexed: 11/23/2022] Open
Abstract
The trifluoromethyl group has been previously explored as a non-conjugated electron-withdrawing group in donor–acceptor thermally activated delayed fluorescence (TADF) emitters. In the present study, we investigate computationally the potential of other fluorine-containing acceptors, trifluoromethoxy (OCF3), trifluoromethylthio (SCF3), and pentafluorosulfanyl (SF5), within two families of donor–acceptor TADF emitters. Time-dependent density functional theory calculations indicate that when only two ortho-disposed carbazole donors are used (Type I molecules), the lowest-lying triplet state possesses locally excited (LE) character while the lowest-lying singlet state possesses charge-transfer character. When five carbazole donors are present in the emitter design (Type II molecules), now both S1 and T1 states possess CT character. For molecules 2CzOCF3 and 5CzOCF3, the singlet energies are predicted to be 3.92 eV and 3.45 eV; however, the singlet-triplet energy gaps, ΔESTs, are predicted to be large at 0.46 eV and 0.37 eV, respectively. The compounds 2CzCF3, 2CzSCF3, and 2CzSF5, from Type I molecules, show significant promise as deep blue TADF emitters, possessing high calculated singlet energies in the gas phase (3.62 eV, 3.66 eV, and 3.51 eV, respectively) and small, ΔESTs, of 0.17 eV, 0.22 eV, and 0.07 eV, respectively. For compounds 5CzSCF3 and 5CzSF5, from Type II molecules, the singlet energies are stabilized to 3.24 eV and 3.00 eV, respectively, while ΔESTs are 0.27 eV and 0.12 eV, respectively, thus both show promise as blue or sky-blue TADF emitters. All these six molecules possess a dense number of intermediate excited states between S1 and T1, thus likely leading to a very efficient reverse intersystem crossing in these compounds.
Collapse
Affiliation(s)
- Dongyang Chen
- Organic Semiconductor Centre, EaStCHEM School of Chemistry, University of St Andrews, St Andrews, Fife, KY16 9ST, UK
| | - Eli Zysman-Colman
- Organic Semiconductor Centre, EaStCHEM School of Chemistry, University of St Andrews, St Andrews, Fife, KY16 9ST, UK
| |
Collapse
|
16
|
Woo SJ, Kim JJ. TD-DFT and Experimental Methods for Unraveling the Energy Distribution of Charge-Transfer Triplet/Singlet States of a TADF Molecule in a Frozen Matrix. J Phys Chem A 2021; 125:1234-1242. [PMID: 33517658 DOI: 10.1021/acs.jpca.0c11322] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Reverse intersystem crossing (RISC) rate of a thermally activated delayed fluorescence (TADF) molecule is sensitive to the energy alignment of the singlet charge-transfer state (1CT), triplet charge-transfer state (3CT), and locally excited triplet state (3LE). However, the energy distribution of the charge-transfer states originating from the conformational distribution of TADF molecules in a solid matrix inevitably generated during the preparation of a solid sample due to the rotatable donor-acceptor linkage is rarely considered. Moreover, the investigation of the energy distribution of the 3CT state is both theoretically and experimentally difficult due to the triplet instabilities of time-dependent density functional (TD-DFT) calculations and difficulties in phosphorescence measurements, respectively. As a result, the relationships between conformational distribution, configurations of excited state transition orbitals, and excited state energies/dynamics have not been clearly explained. In this work, we determined the energy distribution of CT states of the TADF emitter TPSA in frozen toluene at 77 K by the measurement of time-resolved spectra in the full time range (1 ns to 30 s) of emission including prompt fluorescence, TADF, 3CT phosphorescence, and 3LE phosphorescence. We obtained the energy band of CT states where 1CT and 3CT states are distributed in the range of 2.85-3.00 and 2.64-2.96 eV, respectively. We tested various global hybrid and long-range corrected functionals for the TD-DFT calculation of 3CT energy of TPSA and found that only the M11 functional shows consistent results without triplet instability. We performed TD-DFT with the M11* functional optimized for a robust dihedral angle scan of 3CT states without triplet instability and reproduced the energy band structure obtained from the experiment. Through TD-DFT and experimental investigations, it is estimated that the dihedral angles of donor-acceptor (θD-A) and acceptor-linker (θA) of TPSA in frozen toluene lie within the range 70° ≤ θD-A ≤ 90° and 0° ≤ θA ≤ 30° respectively. Our results show that the dihedral angle distribution must be considered for further investigation of the photophysics of TADF molecules and the development of stable and efficient TADF emitters.
Collapse
Affiliation(s)
- Seung-Je Woo
- Department of Materials Science and Engineering, Seoul National University, Seoul 08826, Republic of Korea
| | - Jang-Joo Kim
- Department of Materials Science and Engineering, Seoul National University, Seoul 08826, Republic of Korea
| |
Collapse
|
17
|
Ma Y, Zhang K, Zhang Y, Song Y, Lin L, Wang CK, Fan J. Effects of Secondary Acceptors on Excited-State Properties of Sky-Blue Thermally Activated Delayed Fluorescence Molecules: Luminescence Mechanism and Molecular Design. J Phys Chem A 2021; 125:175-186. [PMID: 33373223 DOI: 10.1021/acs.jpca.0c08994] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The development of efficient sky-blue thermally activated delayed fluorescence (TADF) emitters is highly desired. However, the types and amounts of sky-blue TADF are far from meeting the requirements, and effective molecular design strategies are expected. Herein, the photophysical properties and excited-state dynamics of 12 molecules are theoretically studied based on the thermal vibration correlation function method. Distributions of holes and electrons are analyzed by the heat maps. The frontier molecular orbital distribution, adiabatic singlet-triplet energy gap, and reorganization energy are analyzed in detail. Furthermore, the radiative and non-radiative as well as the intersystem crossing (ISC) and reverse intersystem crossing (RISC) processes are studied, and the up-conversion process is illustrated. Our results indicate that different substitution positions and numbers play an important role in the luminescence properties of TADF molecules. The meta-position substitutions restrict the geometry variations, hinder the non-radiative energy consumption process, and promote the radiative process of TADF molecules. Meanwhile, molecules with ortho-position substitutions possess the smallest energy gaps (ΔEst) and the largest RISC rates. Moreover, molecules with the substitutions of one tBCz group and two PO groups have the smallest ΔEst and the largest spin orbital coupling. Thus, a wise molecular design strategy, namely, ortho-position substitutions as well as substitutions with one tBCz group and two PO groups, is proposed to facilitate the RISC process. Based on this rule, new efficient TADF molecules are theoretically designed and proposed. Our work reasonably elucidates the experimental measurements, and the effects of different substitution numbers and positions of secondary acceptors on TADF properties are highlighted, which could provide a theoretical perspective for designing efficient sky-blue TADF molecules.
Collapse
Affiliation(s)
- Yuying Ma
- Shandong Province Key Laboratory of Medical Physics and Image Processing Technology, Institute of Materials and Clean Energy, School of Physics and Electronics, Shandong Normal University, Jinan 250014, China
| | - Kai Zhang
- Shandong Province Key Laboratory of Medical Physics and Image Processing Technology, Institute of Materials and Clean Energy, School of Physics and Electronics, Shandong Normal University, Jinan 250014, China
| | - Yuchen Zhang
- Shandong Province Key Laboratory of Medical Physics and Image Processing Technology, Institute of Materials and Clean Energy, School of Physics and Electronics, Shandong Normal University, Jinan 250014, China
| | - Yuzhi Song
- Shandong Province Key Laboratory of Medical Physics and Image Processing Technology, Institute of Materials and Clean Energy, School of Physics and Electronics, Shandong Normal University, Jinan 250014, China
| | - Lili Lin
- Shandong Province Key Laboratory of Medical Physics and Image Processing Technology, Institute of Materials and Clean Energy, School of Physics and Electronics, Shandong Normal University, Jinan 250014, China
| | - Chuan-Kui Wang
- Shandong Province Key Laboratory of Medical Physics and Image Processing Technology, Institute of Materials and Clean Energy, School of Physics and Electronics, Shandong Normal University, Jinan 250014, China
| | - Jianzhong Fan
- Shandong Province Key Laboratory of Medical Physics and Image Processing Technology, Institute of Materials and Clean Energy, School of Physics and Electronics, Shandong Normal University, Jinan 250014, China.,Guangdong Provincial Key Laboratory of Luminescence from Molecular Aggregates, South China University of Technology, Guangzhou 510640, China
| |
Collapse
|
18
|
Dhali R, Phan Huu DKA, Bertocchi F, Sissa C, Terenziani F, Painelli A. Understanding TADF: a joint experimental and theoretical study of DMAC-TRZ. Phys Chem Chem Phys 2021; 23:378-387. [DOI: 10.1039/d0cp05982j] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
TADF offers a promising way to harvest triplets in OLED for improved efficiency. To concurrently optimize the dye inside the matrix, a thorough experimental and theoretical study is presented of a the TADF dye addressing environmental effects.
Collapse
Affiliation(s)
- Rama Dhali
- Department of Chemistry
- Life Science and Environmental Sustainability
- University of Parma
- 43124 Parma
- Italy
| | - D. K. Andrea Phan Huu
- Department of Chemistry
- Life Science and Environmental Sustainability
- University of Parma
- 43124 Parma
- Italy
| | - Francesco Bertocchi
- Department of Chemistry
- Life Science and Environmental Sustainability
- University of Parma
- 43124 Parma
- Italy
| | - Cristina Sissa
- Department of Chemistry
- Life Science and Environmental Sustainability
- University of Parma
- 43124 Parma
- Italy
| | - Francesca Terenziani
- Department of Chemistry
- Life Science and Environmental Sustainability
- University of Parma
- 43124 Parma
- Italy
| | - Anna Painelli
- Department of Chemistry
- Life Science and Environmental Sustainability
- University of Parma
- 43124 Parma
- Italy
| |
Collapse
|
19
|
Avellanal‐Zaballa E, Prieto‐Castañeda A, García‐Garrido F, Agarrabeitia AR, Rebollar E, Bañuelos J, García‐Moreno I, Ortiz MJ. Red/NIR Thermally Activated Delayed Fluorescence from Aza‐BODIPYs. Chemistry 2020; 26:16080-16088. [DOI: 10.1002/chem.202002916] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2020] [Revised: 07/19/2020] [Indexed: 11/10/2022]
Affiliation(s)
| | | | | | | | - Esther Rebollar
- Dpto, de Sistemas de Baja Dimensionalidad, Superficies y Materia Condensada Instituto Química-Física “Rocasolano”, IQFR-CSIC Serrano 119 28006 Madrid Spain
| | - Jorge Bañuelos
- Dpto. Química Física Universidad del País Vasco (UPV/EHU) Aptdo 644 48080 Bilbao Spain
| | - Inmaculada García‐Moreno
- Dpto, de Sistemas de Baja Dimensionalidad, Superficies y Materia Condensada Instituto Química-Física “Rocasolano”, IQFR-CSIC Serrano 119 28006 Madrid Spain
| | - María J. Ortiz
- Dpto. Química Orgánica Universidad Complutense Ciudad Universitaria s/n 28006 Madrid Spain
| |
Collapse
|
20
|
Han P, Lin C, Ma D, Qin A, Tang BZ. A Tetraphenylbenzene‐Based AIE Luminogen with Donor‐Acceptor Structure: Unique Mechanochromic Emission and High Exciton Utilization. ASIAN J ORG CHEM 2020. [DOI: 10.1002/ajoc.202000133] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Pengbo Han
- State Key Laboratory of Luminescent Materials and Devices Guangdong Provincial Key Laboratory of Luminescence from Molecular Aggregates Center for Aggregation-Induced EmissionSouth China University of Technology Guangzhou 510640 China
| | - Chengwei Lin
- State Key Laboratory of Luminescent Materials and Devices Guangdong Provincial Key Laboratory of Luminescence from Molecular Aggregates Center for Aggregation-Induced EmissionSouth China University of Technology Guangzhou 510640 China
| | - Dongge Ma
- State Key Laboratory of Luminescent Materials and Devices Guangdong Provincial Key Laboratory of Luminescence from Molecular Aggregates Center for Aggregation-Induced EmissionSouth China University of Technology Guangzhou 510640 China
| | - Anjun Qin
- State Key Laboratory of Luminescent Materials and Devices Guangdong Provincial Key Laboratory of Luminescence from Molecular Aggregates Center for Aggregation-Induced EmissionSouth China University of Technology Guangzhou 510640 China
| | - Ben Zhong Tang
- State Key Laboratory of Luminescent Materials and Devices Guangdong Provincial Key Laboratory of Luminescence from Molecular Aggregates Center for Aggregation-Induced EmissionSouth China University of Technology Guangzhou 510640 China
- Department of Chemistry Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and ReconstructionThe Hong Kong University of Science and Technology Clear Water Bay, Kowloon Hong Kong 999077 China
| |
Collapse
|
21
|
Che W, Xie Y, Li Z. Structural Design of Blue‐to‐Red Thermally‐Activated Delayed Fluorescence Molecules by Adjusting the Strength between Donor and Acceptor. ASIAN J ORG CHEM 2020. [DOI: 10.1002/ajoc.202000128] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Affiliation(s)
- Weilong Che
- Institute of Molecular Aggregation ScienceTianjin University Tianjin 300072 P. R. China)
| | - Yujun Xie
- Institute of Molecular Aggregation ScienceTianjin University Tianjin 300072 P. R. China)
| | - Zhen Li
- Institute of Molecular Aggregation ScienceTianjin University Tianjin 300072 P. R. China)
- Sauvage Center for Molecular SciencesDepartment of ChemistryWuhan University Wuhan 430072 P. R. China
| |
Collapse
|
22
|
Jena S, Dhanalakshmi P, Bano G, Thilagar P. Delayed Fluorescence, Room Temperature Phosphorescence, and Mechanofluorochromic Naphthalimides: Differential Imaging of Normoxia and Hypoxia Live Cancer Cells. J Phys Chem B 2020; 124:5393-5406. [PMID: 32501697 DOI: 10.1021/acs.jpcb.0c04115] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We study the effect of molecular conformation on the electronic coupling between the donor amines and acceptor 1,8-naphthalimide (NPI) in a series of D-A systems 1-4 (A = NPI; D = phenothiazine, phenoxazine, carbazole, diphenylamine, respectively, for 1, 2, 3, and 4). Weakly coupled systems show dual emission in the solution state, while strongly coupled systems show single emission bands. The energy of transitions and photoluminescence (PL) quantum yield are sensitive to the molecular conformation and donor strength. These compounds show delayed emission in the solutions and aggregated state and phosphorescence in the solid state. Compounds 3 and 4 with weak donors exhibit intermolecular slipped π···π interactions in the solid state and consequently exhibit dual (intra- and inter-) phosphorescence at low temperature. Steady state and time-resolved PL studies at variable temperature together with computational and crystal structure analysis were used to rationalize the optical properties of these compounds. The delayed emission of these compounds is sensitive to molecular oxygen; accordingly, these molecules are utilized for differential imaging of normoxia and hypoxia cancer cells.
Collapse
Affiliation(s)
- Satyam Jena
- Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bangalore, India 560012
| | - Pandi Dhanalakshmi
- Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bangalore, India 560012
| | - Gulista Bano
- Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bangalore, India 560012
| | - Pakkirisamy Thilagar
- Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bangalore, India 560012
| |
Collapse
|
23
|
Ai Q, Chai J, Lou W, Liu T, Wang D, Deng C, Wang C, Li G, Liu X, Liu Z, Zhang Q. Efficient and Stable Organic Light-Emitting Diodes Employing Indolo[2,3- b]indole-Based Thermally Activated Delayed Fluorescence Emitters. ACS APPLIED MATERIALS & INTERFACES 2020; 12:6127-6136. [PMID: 31847516 DOI: 10.1021/acsami.9b19474] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Triplet excitons can be effectively harvested in organic light-emitting diodes employing thermally activated delayed fluorescence (TADF) molecules as the emitter and host. A design strategy for blue and green emitters with small S1-T1 splitting (ΔEST) is to construct a donor-acceptor (D-A) type molecule with moieties combining a high T1 level with a strong electron-donating/withdrawing character. Here, we report a new kind of TADF emitter with an indolo[2,3-b]indole (IDID) donor. In comparison to other reported indolocarbazole and indoloindole donors, IDID has a higher T1 level, which is comparable to that of the classical donor 9,9-dimethyl-9,10-dihydroacridine (DMAC) for blue TADF emitters. The sky-blue and green TADF emitters based on the IDID donor and a phenyltriazine acceptor exhibit high photoluminescence quantum yields (0.78-0.92) and short TADF lifetimes (1.1-1.7 μs) in doped films. Devices employing these IDID-based emitters offer an external quantum efficiency of 19.2%, which is comparable to that obtained for a device employing an analogous compound with a DMAC donor, while the stability of the former is higher than that of the latter owing to the just-right D-A twisting angles (∼59°) in the IDID-based emitters leading to a balance between ΔEST and the fluorescence rate. The utilization of host materials with a similar polarity to the emitter is found to be an effective strategy to improve device stability.
Collapse
Affiliation(s)
- Qi Ai
- MOE Key Laboratory of Macromolecular Synthesis and Functionalization, Department of Polymer Science and Engineering , Zhejiang University , Hangzhou 310027 , China
- College of Optical and Electronic Technology , China Jiliang University , Hangzhou 310018 , China
| | - Jingshan Chai
- MOE Key Laboratory of Macromolecular Synthesis and Functionalization, Department of Polymer Science and Engineering , Zhejiang University , Hangzhou 310027 , China
| | - Weiwei Lou
- State Key Laboratory Breeding Base of Green Chemistry-Synthesis Technology, College of Chemical Engineering , Zhejiang University of Technology , Hangzhou 310014 , China
| | - Tiangeng Liu
- MOE Key Laboratory of Macromolecular Synthesis and Functionalization, Department of Polymer Science and Engineering , Zhejiang University , Hangzhou 310027 , China
| | - Dan Wang
- MOE Key Laboratory of Macromolecular Synthesis and Functionalization, Department of Polymer Science and Engineering , Zhejiang University , Hangzhou 310027 , China
| | - Chao Deng
- MOE Key Laboratory of Macromolecular Synthesis and Functionalization, Department of Polymer Science and Engineering , Zhejiang University , Hangzhou 310027 , China
| | - Chao Wang
- MOE Key Laboratory of Macromolecular Synthesis and Functionalization, Department of Polymer Science and Engineering , Zhejiang University , Hangzhou 310027 , China
- Singapore University of Technology and Design , 8 Somapah Road , 487372 Singapore
| | - Guijie Li
- State Key Laboratory Breeding Base of Green Chemistry-Synthesis Technology, College of Chemical Engineering , Zhejiang University of Technology , Hangzhou 310014 , China
| | - Xiaogang Liu
- Singapore University of Technology and Design , 8 Somapah Road , 487372 Singapore
| | - Zugang Liu
- College of Optical and Electronic Technology , China Jiliang University , Hangzhou 310018 , China
| | - Qisheng Zhang
- MOE Key Laboratory of Macromolecular Synthesis and Functionalization, Department of Polymer Science and Engineering , Zhejiang University , Hangzhou 310027 , China
| |
Collapse
|
24
|
Li X, Li J, Liu D, Li D, Dong R. A donor design strategy for triazine-carbazole blue thermally activated delayed fluorescence materials. NEW J CHEM 2020. [DOI: 10.1039/d0nj00905a] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Enhancing the delayed emission proportion by incorporating bulky substituent at the 1-site of carbazole donors is proved to be effective and practical strategy to improve the EL performance of cyaphenine-carbazole type blue TADF emitters.
Collapse
Affiliation(s)
- Xin Li
- State Key Laboratory of Fine Chemicals
- College of Chemical Engineering
- Dalian University of Technology
- Dalian
- China
| | - Jiuyan Li
- State Key Laboratory of Fine Chemicals
- College of Chemical Engineering
- Dalian University of Technology
- Dalian
- China
| | - Di Liu
- State Key Laboratory of Fine Chemicals
- College of Chemical Engineering
- Dalian University of Technology
- Dalian
- China
| | - Deli Li
- State Key Laboratory of Fine Chemicals
- College of Chemical Engineering
- Dalian University of Technology
- Dalian
- China
| | - Ruizhi Dong
- State Key Laboratory of Fine Chemicals
- College of Chemical Engineering
- Dalian University of Technology
- Dalian
- China
| |
Collapse
|
25
|
Stachelek P, Ward JS, dos Santos PL, Danos A, Colella M, Haase N, Raynes SJ, Batsanov AS, Bryce MR, Monkman AP. Molecular Design Strategies for Color Tuning of Blue TADF Emitters. ACS APPLIED MATERIALS & INTERFACES 2019; 11:27125-27133. [PMID: 31314484 PMCID: PMC7006999 DOI: 10.1021/acsami.9b06364] [Citation(s) in RCA: 42] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/11/2019] [Accepted: 07/01/2019] [Indexed: 05/24/2023]
Abstract
New thermally activated delayed fluorescence (TADF) blue emitter molecules based on the known donor-acceptor-donor (D-A-D)-type TADF molecule, 2,7-bis(9,9-dimethylacridin-10-yl)-9,9-dimethylthioxanthene-S,S-dioxide (DDMA-TXO2), are reported. The motivation for the present investigation is via the use of rational molecular design, based on DDMA-TXO2, to elevate the organic light emitting diode (OLED) performance and obtain deeper blue color coordinates. To achieve this goal, the strength of the donor (D) unit and acceptor (A) units have been tuned with methyl substituents. The methyl functionality on the acceptor was also expected to modulate the D-A torsion angle in order to obtain a blue shift in the electroluminescence. The effect of regioisomeric structures has also been investigated. Herein, we report the photophysical, electrochemical, and single-crystal X-ray crystallography data to assist with the successful OLED design. The methyl substituents on the DDMA-TXO2 framework have profound effects on the photophysics and color coordinates of the emitters. The weak electron-donating methyl groups alter the redox properties of the D and A units and consequently affect the singlet and triplet levels but not the energy gap (ΔEST). By systematically manipulating all of the aforementioned factors, devices have been obtained with acceptor-substituted III with a maximum external quantum efficiency of 22.6% and Commission Internationale de l'Éclairage coordinates of (0.15, 0.18) at 1000 cd m-2.
Collapse
Affiliation(s)
- Patrycja Stachelek
- Department
of Physics and Department of Chemistry, Durham University, Durham DH1 3LE, U.K.
| | - Jonathan S. Ward
- Department
of Physics and Department of Chemistry, Durham University, Durham DH1 3LE, U.K.
| | - Paloma L. dos Santos
- Department
of Physics and Department of Chemistry, Durham University, Durham DH1 3LE, U.K.
| | - Andrew Danos
- Department
of Physics and Department of Chemistry, Durham University, Durham DH1 3LE, U.K.
| | - Marco Colella
- Department
of Physics and Department of Chemistry, Durham University, Durham DH1 3LE, U.K.
| | - Nils Haase
- Institute
of Physics, Experimental Physics IV, University
of Augsburg, Universitätsstr.
1, Augsburg 86135, Germany
- Merck
KGaA, Performance Materials—Display Solutions, Frankfurter Straße 250, Darmstadt 64293, Germany
| | - Samuel J. Raynes
- Department
of Physics and Department of Chemistry, Durham University, Durham DH1 3LE, U.K.
| | - Andrei S. Batsanov
- Department
of Physics and Department of Chemistry, Durham University, Durham DH1 3LE, U.K.
| | - Martin R. Bryce
- Department
of Physics and Department of Chemistry, Durham University, Durham DH1 3LE, U.K.
| | - Andrew P. Monkman
- Department
of Physics and Department of Chemistry, Durham University, Durham DH1 3LE, U.K.
| |
Collapse
|
26
|
Zhou D, Liu D, Gong X, Ma H, Qian G, Gong S, Xie G, Zhu W, Wang Y. Solution-Processed Highly Efficient Bluish-Green Thermally Activated Delayed Fluorescence Emitter Bearing an Asymmetric Oxadiazole-Difluoroboron Double Acceptor. ACS APPLIED MATERIALS & INTERFACES 2019; 11:24339-24348. [PMID: 31187977 DOI: 10.1021/acsami.9b07511] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Difluoroboron (BF2)-containing dyes have attracted great interest owing to their exceptionally high luminescence efficiency and good electron-withdrawing properties. However, only a few reports on difluoroboron-based thermally activated delayed fluorescence (TADF) have been addressed. In this contribution, a novel BF2-containing TADF molecule of BFOXD, which contains two acceptor fragments of oxadiazole (OXD) and BF2 and one donor unit of 9,9-dimethylacridine, was synthesized and characterized. For comparison, the precursor of OHOXD bearing one acceptor unit was also investigated. Both molecules clearly show TADF characteristics with sky-blue emission in solution and film state. Additionally, OHOXD undergoes excited-state intramolecular proton transfer-coupled intramolecular charge transfer processes. Using 9-(4-tert-butylphenyl)-3,6-bis(triphenylsilyl)-9H-carbazole (CzSi) as the host, the organic light-emitting diodes fabricated via a solution process show maximum external quantum efficiency (EQE) of 2.98 and 13.8% for OHOXD- and BFOXD-based devices, respectively. While the bipolar TADF host of 10-(4-((4-(9H-carbazol-9-yl)phenyl)sulfonyl)phenyl)-9,9-dimethyl-9,10-dihydroacridine (CzAcSF) is utilized instead of CzSi, the OHOXD- and BFOXD-based devices exhibit better performances with the maximum EQEs of 12.1 and 20.1%, respectively, which render the most efficient and the bluest emission ever reported for the BF2-based TADF molecules. This research demonstrates that introduction of one more acceptor unit into the TADF molecule could have a positive effect on emission efficiency, which opens a new way to design high-efficiency TADF molecules.
Collapse
Affiliation(s)
- Di Zhou
- National Experimental Demonstration Center for Materials Science and Engineering, Jiangsu Key Laboratory of Environmentally Friendly Polymeric Materials, Jiangsu Collaborative Innovation Center of Photovoltaic Science and Engineering, Jiangsu Engineering Laboratory of Light-Electricity-Heat Energy-Converting Materials and Applications, School of Materials Science & Engineering , Changzhou University , Changzhou 213164 , China
- College of Chemistry , Xiangtan University , Xiangtan 411105 , China
| | - Denghui Liu
- National Experimental Demonstration Center for Materials Science and Engineering, Jiangsu Key Laboratory of Environmentally Friendly Polymeric Materials, Jiangsu Collaborative Innovation Center of Photovoltaic Science and Engineering, Jiangsu Engineering Laboratory of Light-Electricity-Heat Energy-Converting Materials and Applications, School of Materials Science & Engineering , Changzhou University , Changzhou 213164 , China
| | - Xu Gong
- Hubei Key Lab on Organic and Polymeric Optoelectronic Materials, Department of Chemistry , Wuhan University , Wuhan 430072 , China
| | - Huili Ma
- Key Laboratory of Flexible Electronics (KLOFE) & Institute of Advanced Materials (IAM), Nanjing Tech University (NanjingTech) , 30 South Puzhu Road , Nanjing 211816 , China
| | - Gaowei Qian
- National Experimental Demonstration Center for Materials Science and Engineering, Jiangsu Key Laboratory of Environmentally Friendly Polymeric Materials, Jiangsu Collaborative Innovation Center of Photovoltaic Science and Engineering, Jiangsu Engineering Laboratory of Light-Electricity-Heat Energy-Converting Materials and Applications, School of Materials Science & Engineering , Changzhou University , Changzhou 213164 , China
| | - Shaolong Gong
- Hubei Key Lab on Organic and Polymeric Optoelectronic Materials, Department of Chemistry , Wuhan University , Wuhan 430072 , China
| | - Guohua Xie
- Hubei Key Lab on Organic and Polymeric Optoelectronic Materials, Department of Chemistry , Wuhan University , Wuhan 430072 , China
| | - Weiguo Zhu
- National Experimental Demonstration Center for Materials Science and Engineering, Jiangsu Key Laboratory of Environmentally Friendly Polymeric Materials, Jiangsu Collaborative Innovation Center of Photovoltaic Science and Engineering, Jiangsu Engineering Laboratory of Light-Electricity-Heat Energy-Converting Materials and Applications, School of Materials Science & Engineering , Changzhou University , Changzhou 213164 , China
| | - Yafei Wang
- National Experimental Demonstration Center for Materials Science and Engineering, Jiangsu Key Laboratory of Environmentally Friendly Polymeric Materials, Jiangsu Collaborative Innovation Center of Photovoltaic Science and Engineering, Jiangsu Engineering Laboratory of Light-Electricity-Heat Energy-Converting Materials and Applications, School of Materials Science & Engineering , Changzhou University , Changzhou 213164 , China
- Key Laboratory of Advanced Display and System Applications of Ministry of Education , Shanghai University , 149 Yanchang Road , Shanghai 200072 , China
| |
Collapse
|
27
|
de Sa Pereira D, Menelaou C, Danos A, Marian C, Monkman AP. Electroabsorption Spectroscopy as a Tool for Probing Charge Transfer and State Mixing in Thermally Activated Delayed Fluorescence Emitters. J Phys Chem Lett 2019; 10:3205-3211. [PMID: 31117683 PMCID: PMC7007248 DOI: 10.1021/acs.jpclett.9b00999] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2019] [Accepted: 05/21/2019] [Indexed: 05/24/2023]
Abstract
Solid-state electroabsorption is demonstrated as a powerful tool for probing the charge transfer (CT) character and state mixing in the low-energy optical transitions of two structurally similar thermally activated delayed fluorescent (TADF) materials with divergent photophysical and device performances. The Liptay model is used to fit differentials of the low-energy absorption bands to the measured electroabsorption spectra, with both emitters showing CT characteristics and large changes in dipole moments upon excitation despite the associated absorption bands appearing to be structured. High electric fields then reveal transfer of oscillator strength to a state close to the CT in the better performing molecule. With supporting TDDFT-TDA and DFT/MRCI calculations, this state showed ππ* characteristics of a local acceptor triplet that strongly mixes with the σπ* of the CT. The emitter with poor TADF performance showed no evidence of such mixing.
Collapse
Affiliation(s)
- Daniel de Sa Pereira
- Department
of Physics, Durham University, South Road, Durham DH1 3LE, United
Kingdom
| | - Christopher Menelaou
- Department
of Physics, Durham University, South Road, Durham DH1 3LE, United
Kingdom
| | - Andrew Danos
- Department
of Physics, Durham University, South Road, Durham DH1 3LE, United
Kingdom
| | - Christel Marian
- Institut
für Theoretische Chemie, Heinrich-Heine-Universität, Universitätsstrasse 1, 40225 Düsseldorf, Germany
| | - Andrew P. Monkman
- Department
of Physics, Durham University, South Road, Durham DH1 3LE, United
Kingdom
| |
Collapse
|
28
|
Jayakumar J, Wu TL, Huang MJ, Huang PY, Chou TY, Lin HW, Cheng CH. Pyridine-Carbonitrile-Carbazole-Based Delayed Fluorescence Materials with Highly Congested Structures and Excellent OLED Performance. ACS APPLIED MATERIALS & INTERFACES 2019; 11:21042-21048. [PMID: 31088068 DOI: 10.1021/acsami.9b04664] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Three pyridine-carbonitrile-carbazole-based thermally activated delayed fluorescence (TADF) materials with highly sterically congested structures have been synthesized. The donor-acceptor-type TADF emitters (26-, 246-, and 35tCzPPC) consist of a 2,6-diphenylpyridine-3,5-dicarbonitrile core (PPC) as the acceptor and a di( t-butyl)carbazole-substituted phenyl group attached to C4 of the PC core as the donor. The molecules show a unique structure containing two consecutive large twisted angles along the donor and acceptor groups. The structure leads to a nearly complete space separation of the highest occupied molecular orbital and lowest unoccupied molecular orbital, a small Δ EST value, and excellent TADF property. Moreover, the 26- and 246tCzPPC dopants favor a horizontal alignment enhancing the light outcoupling of the device. In contrast, 35tCzPPC favors a perpendicular alignment reducing the light outcoupling efficiency of the device. The 246tCzPPC-based devices show external quantum efficiency as high as 29.6% because of excellent TADF property, very high photoluminescence quantum yield, and high Θ value in the thin films. The device performance is the best among the pyridine-carbonitrile-based TADF emitters.
Collapse
|
29
|
Wu TL, Liao SY, Huang PY, Hong ZS, Huang MP, Lin CC, Cheng MJ, Cheng CH. Exciplex Organic Light-Emitting Diodes with Nearly 20% External Quantum Efficiency: Effect of Intermolecular Steric Hindrance between the Donor and Acceptor Pair. ACS APPLIED MATERIALS & INTERFACES 2019; 11:19294-19300. [PMID: 31046225 DOI: 10.1021/acsami.9b04365] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Exciplex emitters have emerged as an important class of thermally activated delayed fluorescence (TADF) materials for highly efficient OLEDs. A TADF exciplex emitter requires an intermolecular donor/acceptor pair. We have synthesized a bipolar donor-type material, DPSTPA, which was used to pair with known acceptor materials (2CzPN, 4CzIPN, or CzDBA). The OLEDs based on the exciplex emitters, DPSTPA/X, where X = 2CzPN and CzDBA, give green and orange-red colors with record-high external quantum efficiencies (EQEs) of 19.0 ± 0.6 and 14.6 ± 0.4%, respectively. In contrast, the exciplex pair DPSTPA/4CzIPN gave a very low photoluminescence quantum yield (PLQY) and a very low EQE value of the device. The DFT calculations indicate that the intermolecular distance between the donor and the acceptor plays a key factor for the PLQY and EQE. The observed low PLQY and the poor device performance for the DPSTPA/4CzIPN pair are probably because of the relatively long distance between the DPSTPA and 4CzIPN in the thin film caused by the four congested carbazole (Cz) groups of 4CzIPN, which effectively block the interaction of the nitrile acceptor with the triphenylamino donor of DPSTPA.
Collapse
Affiliation(s)
- Tien-Lin Wu
- Department of Chemistry , National Tsing Hua University , No. 101, Section 2, Kuang-Fu Road , Hsinchu 30013 , Taiwan
| | - Ssu-Yu Liao
- Department of Chemistry , National Tsing Hua University , No. 101, Section 2, Kuang-Fu Road , Hsinchu 30013 , Taiwan
| | - Pei-Yun Huang
- Department of Chemistry , National Tsing Hua University , No. 101, Section 2, Kuang-Fu Road , Hsinchu 30013 , Taiwan
| | - Zih-Siang Hong
- Department of Chemistry , National Cheng Kung University No. 1, Daxue Road , East District, Tainan 70101 , Taiwan
| | - Man-Ping Huang
- Department of Chemistry , National Tsing Hua University , No. 101, Section 2, Kuang-Fu Road , Hsinchu 30013 , Taiwan
| | - Chih-Chun Lin
- Department of Chemistry , National Tsing Hua University , No. 101, Section 2, Kuang-Fu Road , Hsinchu 30013 , Taiwan
| | - Mu-Jeng Cheng
- Department of Chemistry , National Cheng Kung University No. 1, Daxue Road , East District, Tainan 70101 , Taiwan
| | - Chien-Hong Cheng
- Department of Chemistry , National Tsing Hua University , No. 101, Section 2, Kuang-Fu Road , Hsinchu 30013 , Taiwan
| |
Collapse
|
30
|
Liu J, Zhou K, Wang D, Deng C, Duan K, Ai Q, Zhang Q. Pyrazine-Based Blue Thermally Activated Delayed Fluorescence Materials: Combine Small Singlet-Triplet Splitting With Large Fluorescence Rate. Front Chem 2019; 7:312. [PMID: 31165054 PMCID: PMC6536661 DOI: 10.3389/fchem.2019.00312] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2019] [Accepted: 04/18/2019] [Indexed: 01/21/2023] Open
Abstract
Metal-free thermally activated delayed fluorescence (TADF) emitters have emerged as promising candidate materials for highly efficient and low-cost organic light-emitting diodes (OLEDs). Here, a novel acceptor 2-cyanopyrazine is selected for the construction of blue TADF molecules via computer-assisted molecular design. Both theoretical prediction and experimental photophysical data indicate a small S1-T1 energy gap (ΔEST) and a relative large fluorescence rate (kF) in an o-phenylene-bridged 2-cyanopyrazine/3,6-di-tert-butylcarbazole compound (TCzPZCN). The kF value of 3.7 × 107 s−1 observed in a TCzPZCN doped film is among the highest in the TADF emitters with a ΔEST smaller than 0.1 eV. Blue TADF emission is observed in a TCzPZCN doped film with a short TADF lifetime of 1.9 μs. The OLEDs using TCzPZCN as emitter exhibit a maximum external quantum efficiency (EQE) of 7.6% with low-efficiency roll-off. A sky-blue device containing a derivative of TCzPZCN achieves an improved EQE maximum of 12.2% by suppressing the non-radiative decay at T1.
Collapse
Affiliation(s)
- Junyuan Liu
- MOE Key Laboratory of Macromolecular Synthesis and Functionalization, Department of Polymer Science and Engineering, Zhejiang University, Hangzhou, China
| | - Keren Zhou
- MOE Key Laboratory of Macromolecular Synthesis and Functionalization, Department of Polymer Science and Engineering, Zhejiang University, Hangzhou, China
| | - Dan Wang
- MOE Key Laboratory of Macromolecular Synthesis and Functionalization, Department of Polymer Science and Engineering, Zhejiang University, Hangzhou, China
| | - Chao Deng
- MOE Key Laboratory of Macromolecular Synthesis and Functionalization, Department of Polymer Science and Engineering, Zhejiang University, Hangzhou, China
| | - Ke Duan
- MOE Key Laboratory of Macromolecular Synthesis and Functionalization, Department of Polymer Science and Engineering, Zhejiang University, Hangzhou, China
| | - Qi Ai
- MOE Key Laboratory of Macromolecular Synthesis and Functionalization, Department of Polymer Science and Engineering, Zhejiang University, Hangzhou, China
| | - Qisheng Zhang
- MOE Key Laboratory of Macromolecular Synthesis and Functionalization, Department of Polymer Science and Engineering, Zhejiang University, Hangzhou, China
| |
Collapse
|
31
|
Wu TL, Lo SH, Chang YC, Huang MJ, Cheng CH. Steric Switching for Thermally Activated Delayed Fluorescence by Controlling the Dihedral Angles between Donor and Acceptor in Organoboron Emitters. ACS APPLIED MATERIALS & INTERFACES 2019; 11:10768-10776. [PMID: 30777421 DOI: 10.1021/acsami.8b21568] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Five emitters CzAZB, tBuCzAZB, tmCzAZB, dmAcAZB, and PxzAZB based on dibenzo-1,4-azaborine as the electron acceptors and two identical amine groups as the donors were designed and synthesized. The dihedral angles between the planes of dibenzo-1,4-azaborine acceptors and amine-based donors greatly affect the thermally activated delayed fluorescence (TADF) property of these materials. A simple concept "steric switching" is introduced to predict whether the emitter possesses TADF property. CzAZB and tBuCzAZB, with very high photoluminescence quantum yields (PLQYs) but small dihedral angles, do not show TADF. In contrast, tmCzAZB reveals a PLQY of only 56% but with a large dihedral angle due to the presence of two methyl groups at C1 and C8 of the carbazole groups, the steric switching operates, and the compound shows TADF property with a deep-blue color having CIE coordinates of (0.14, 0.15). In a similar manner, in dmAcAZB and PxzAZB with high PLQYs and large dihedral angles between the donor and acceptor planes, the "TADF steric switch" readily operates to achieve device external quantum efficiencies as high as 20.8 ± 1.2 and 27.5 ± 1.9% with blue and green emissions, respectively.
Collapse
Affiliation(s)
- Tien-Lin Wu
- Department of Chemistry , National Tsing Hua University , No. 101, Section 2, Kuang-Fu Road , Hsinchu 30013 , Taiwan
| | - Shih-Han Lo
- Department of Chemistry , National Tsing Hua University , No. 101, Section 2, Kuang-Fu Road , Hsinchu 30013 , Taiwan
| | - Yu-Che Chang
- Department of Chemistry , National Tsing Hua University , No. 101, Section 2, Kuang-Fu Road , Hsinchu 30013 , Taiwan
| | - Min-Jie Huang
- Department of Chemistry , National Tsing Hua University , No. 101, Section 2, Kuang-Fu Road , Hsinchu 30013 , Taiwan
| | - Chien-Hong Cheng
- Department of Chemistry , National Tsing Hua University , No. 101, Section 2, Kuang-Fu Road , Hsinchu 30013 , Taiwan
| |
Collapse
|
32
|
Liang X, Tu ZL, Zheng YX. Thermally Activated Delayed Fluorescence Materials: Towards Realization of High Efficiency through Strategic Small Molecular Design. Chemistry 2019; 25:5623-5642. [PMID: 30648301 DOI: 10.1002/chem.201805952] [Citation(s) in RCA: 125] [Impact Index Per Article: 25.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2018] [Indexed: 12/22/2022]
Abstract
Thermally activated delayed fluorescence (TADF) is one of the most intriguing and promising discoveries towards realization of highly-efficient organic light emitting diodes (OLED) utilizing small molecules as emitters. It has the capability of manifesting all excitons generated during the electroluminescent processes, consequently achieving 100 % of internal quantum efficiency. Since the report of the first efficient OLED based on a TADF small molecule in 2012 by Adachi et al., the quest for optimal TADF materials for OLED application has never stopped. Various TADF molecules bearing different design concepts and strategies have been designed and produced, with the aim to boost the overall performances of corresponding OLEDs. In this minireview, the general principles of TADF molecular design based on three basic categories of TADF species: twisted intramolecular charge transfer (TICT), through-space charge transfer (TSCT) and multi-resonance induced TADF (MR-TADF) are discussed in detail. Several key aspects with respect to each category, as well as some effective methods to enhance the efficiency of TADF materials and corresponding OLEDs from the molecular engineering perspectives, are summarized and discussed to exhibit a general landscape of TADF molecular design to a wide variety of scientific researchers within this particular disciplinary area.
Collapse
Affiliation(s)
- Xiao Liang
- State Key Laboratory of Coordination Chemistry, Jiangsu Key Laboratory of Advanced Organic Materials, Collaborative Innovation Center of Advanced Microstructures, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, 210093, P. R. China
| | - Zhen-Long Tu
- State Key Laboratory of Coordination Chemistry, Jiangsu Key Laboratory of Advanced Organic Materials, Collaborative Innovation Center of Advanced Microstructures, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, 210093, P. R. China
| | - You-Xuan Zheng
- State Key Laboratory of Coordination Chemistry, Jiangsu Key Laboratory of Advanced Organic Materials, Collaborative Innovation Center of Advanced Microstructures, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, 210093, P. R. China
| |
Collapse
|
33
|
Marghad I, Bencheikh F, Wang C, Manolikakes S, Rérat A, Gosmini C, Kim DH, Ribierre JC, Adachi C. Control of the dual emission from a thermally activated delayed fluorescence emitter containing phenothiazine units in organic light-emitting diodes. RSC Adv 2019; 9:4336-4343. [PMID: 35520152 PMCID: PMC9060425 DOI: 10.1039/c8ra10393c] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2018] [Accepted: 01/18/2019] [Indexed: 11/21/2022] Open
Abstract
A novel TADF emitter showing dual emission is synthesized and applied to OLEDs with an external quantum efficiency of 11.5%.
Collapse
Affiliation(s)
- Ikbal Marghad
- Center for Organic Photonics and Electronics Research (OPERA)
- Kyushu University
- Fukuoka 819-0395
- Japan
- Laboratoire de chimie moléculaire LCM
| | - Fatima Bencheikh
- Center for Organic Photonics and Electronics Research (OPERA)
- Kyushu University
- Fukuoka 819-0395
- Japan
- Japan Science and Technology Agency (JST)
| | - Chao Wang
- Department of Polymer Science and Engineering
- Zhejiang University
- Hangzhou 310027
- China
| | | | - Alice Rérat
- Laboratoire de chimie moléculaire LCM
- Ecole Polytechnique
- CNRS
- France
| | - Corinne Gosmini
- Laboratoire de chimie moléculaire LCM
- Ecole Polytechnique
- CNRS
- France
| | - Dae hyeon Kim
- Center for Organic Photonics and Electronics Research (OPERA)
- Kyushu University
- Fukuoka 819-0395
- Japan
- Japan Science and Technology Agency (JST)
| | - Jean-Charles Ribierre
- Center for Organic Photonics and Electronics Research (OPERA)
- Kyushu University
- Fukuoka 819-0395
- Japan
- Japan Science and Technology Agency (JST)
| | - Chihaya Adachi
- Center for Organic Photonics and Electronics Research (OPERA)
- Kyushu University
- Fukuoka 819-0395
- Japan
- Japan Science and Technology Agency (JST)
| |
Collapse
|