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Min BK, Kang J, Park JW, Park SW, Ji J, Won C, Im H, Baek Y, Yoo S, Rhee YM. Influence of Spin-Dependent Polaron Pair Charge Recombination Rates on Singlet Exciton Yields of Fluorescent Organic Light-Emitting Diode Materials. J Phys Chem A 2025; 129:3445-3454. [PMID: 40197019 DOI: 10.1021/acs.jpca.4c08704] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/09/2025]
Abstract
Hot exciton materials have been recently studied toward improving the efficiency of fluorescent organic light-emitting diodes (OLEDs). The improvement is achieved by harvesting triplet excitons through high-lying reverse intersystem crossing (hRISC), and for its success, it is necessary to suppress internal conversion (IC) from the spin-converting high-lying triplet state to any lower triplet states. Kasha's rule dictates that such a process is not highly likely, and indeed, there is no direct evidence on inhibited triplet IC. Here, we suggest spin conversion in polaron pairs (PPs) as another channel that can also enhance singlet exciton generation. In our model, the spin states may interconvert by hyperfine coupling and the singlet exciton yields can be influenced by the relative rates of charge recombination of singlet and triplet PPs. We calculate the rate constants of the charge recombination, IC, ISC, and hRISC processes of hot exciton molecules and apply them to generate a kinetic picture via the kinetic master equation, toward examining changes in singlet exciton yields. The results show increases in the singlet exciton generation when the recombination within triplet PP is slower than within singlet PP and when that recombination occurs at a rate comparable to or slower than the hyperfine coupling-induced spin conversion. Additionally, correlation analyses demonstrate that although electronic coupling predominantly determines charge recombination rates, the energy barriers still contribute significantly, manifesting the need of considering both coupling and energy barriers during charge recombination processes in PPs.
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Affiliation(s)
- Byeong Ki Min
- Department of Chemistry, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Korea
| | - Jiseung Kang
- Department of Chemistry, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Korea
| | - Jae Whee Park
- Department of Chemistry, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Korea
| | - Soo Wan Park
- Department of Chemistry, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Korea
| | - Jeoungmin Ji
- School of Electrical Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Korea
| | - Changhyeon Won
- Department of Chemistry, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Korea
| | - Haneul Im
- Department of Chemistry, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Korea
| | - Yunjung Baek
- Department of Chemistry, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Korea
| | - Seunghyup Yoo
- School of Electrical Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Korea
- Graduate School of Semiconductor Technology, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Korea
| | - Young Min Rhee
- Department of Chemistry, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Korea
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Deng Z, Luo Y, Huang G, He J, Phillips DL. Ultrafast Spectroscopic Investigation of the Aggregation Induced TADF from High-Level Reversed Intersystem Crossing. J Phys Chem Lett 2024; 15:11657-11663. [PMID: 39540870 DOI: 10.1021/acs.jpclett.4c02395] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2024]
Abstract
The thermally activated delayed fluorescence (TADF) originating from high-level intersystem crossing (hRISC) presents great potential in realizing a more full utilization of triplet excitons. In this study, DPA-FBP and TPA-FBP were doped in a PMMA film with different weight fractions to study the effect of aggregation on the luminescence properties. As a result, the TADF feature from hRISC was only found in the 50 wt % doped film, whereas the 1 wt % doped film only shows prompt fluorescence. The fs-TA spectroscopy results reveal that the 50 wt % film will generate charge transfer species to lower the energy gap, so that the high-lying triplet exciton can transition back to the singlet state, whereas that of the 1 wt % film will quickly transition to the lowest triplet state due to the unfavorable energy splitting. This study provides a new insight into aggregation effects on the excited-state properties of hot exciton materials and the solid-state photodynamic.
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Affiliation(s)
- Ziqi Deng
- Department of Chemistry, The University of Hong Kong, Pokfulam, Hong Kong 999077, China
| | - Yunfeng Luo
- Department of Chemistry, The University of Hong Kong, Pokfulam, Hong Kong 999077, China
| | - Guanheng Huang
- Department of Chemistry, The University of Hong Kong, Pokfulam, Hong Kong 999077, China
| | - Jiaxing He
- Department of Chemistry, The University of Hong Kong, Pokfulam, Hong Kong 999077, China
| | - David Lee Phillips
- Department of Chemistry, The University of Hong Kong, Pokfulam, Hong Kong 999077, China
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Lin S, Ma Z, Ji X, Zhou Q, Chu W, Zhang J, Liu Y, Han Y, Lian L, Jia M, Chen X, Wu D, Li X, Zhang Y, Shan C, Shi Z. Efficient Large-Area (81 cm 2) Ternary Copper Halides Light-Emitting Diodes with External Quantum Efficiency Exceeding 13% via Host-Guest Strategy. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2024; 36:e2313570. [PMID: 38693828 DOI: 10.1002/adma.202313570] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/12/2023] [Revised: 04/30/2024] [Indexed: 05/03/2024]
Abstract
Ternary copper (Cu) halides are promising candidates for replacing toxic lead halides in the field of perovskite light-emitting diodes (LEDs) toward practical applications. However, the electroluminescent performance of Cu halide-based LEDs remains a great challenge due to the presence of serious nonradiative recombination and inefficient charge transport in Cu halide emitters. Here, the rational design of host-guest [dppb]2Cu2I2 (dppb denotes 1,2-bis[diphenylphosphino]benzene) emitters and its utility in fabricating efficient Cu halide-based green LEDs that show a high external quantum efficiency (EQE) of 13.39% are reported. The host-guest [dppb]2Cu2I2 emitters with mCP (1,3-bis(N-carbazolyl)benzene) host demonstrate a significant improvement of carrier radiative recombination efficiency, with the photoluminescence quantum yield increased by nearly ten times, which is rooted in the efficient energy transfer and type-I energy level alignment between [dppb]2Cu2I2 and mCP. Moreover, the charge-transporting mCP host can raise the carrier mobility of [dppb]2Cu2I2 films, thereby enhancing the charge transport and recombination. More importantly, this strategy enables a large-area prototype LED with a record-breaking area up to 81 cm2, along with a decent EQE of 10.02% and uniform luminance. It is believed these results represent an encouraging stepping stone to bring Cu halide-based LEDs from the laboratory toward commercial lighting and display panels.
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Affiliation(s)
- Shuailing Lin
- Key Laboratory of Materials Physics of Ministry of Education, School of Physics, Zhengzhou University, Daxue Road 75, Zhengzhou, 450052, China
| | - Zhuangzhuang Ma
- Key Laboratory of Materials Physics of Ministry of Education, School of Physics, Zhengzhou University, Daxue Road 75, Zhengzhou, 450052, China
| | - Xinzhen Ji
- Key Laboratory of Materials Physics of Ministry of Education, School of Physics, Zhengzhou University, Daxue Road 75, Zhengzhou, 450052, China
| | - Qicong Zhou
- Key Laboratory of Materials Physics of Ministry of Education, School of Physics, Zhengzhou University, Daxue Road 75, Zhengzhou, 450052, China
| | - Weihong Chu
- Key Laboratory of Materials Physics of Ministry of Education, School of Physics, Zhengzhou University, Daxue Road 75, Zhengzhou, 450052, China
| | - Jibin Zhang
- Key Laboratory of Materials Physics of Ministry of Education, School of Physics, Zhengzhou University, Daxue Road 75, Zhengzhou, 450052, China
| | - Ying Liu
- Key Laboratory of Materials Physics of Ministry of Education, School of Physics, Zhengzhou University, Daxue Road 75, Zhengzhou, 450052, China
| | - Yanbing Han
- Key Laboratory of Materials Physics of Ministry of Education, School of Physics, Zhengzhou University, Daxue Road 75, Zhengzhou, 450052, China
| | - Linyuan Lian
- Key Laboratory of Materials Physics of Ministry of Education, School of Physics, Zhengzhou University, Daxue Road 75, Zhengzhou, 450052, China
| | - Mochen Jia
- Key Laboratory of Materials Physics of Ministry of Education, School of Physics, Zhengzhou University, Daxue Road 75, Zhengzhou, 450052, China
| | - Xu Chen
- Key Laboratory of Materials Physics of Ministry of Education, School of Physics, Zhengzhou University, Daxue Road 75, Zhengzhou, 450052, China
| | - Di Wu
- Key Laboratory of Materials Physics of Ministry of Education, School of Physics, Zhengzhou University, Daxue Road 75, Zhengzhou, 450052, China
| | - Xinjian Li
- Key Laboratory of Materials Physics of Ministry of Education, School of Physics, Zhengzhou University, Daxue Road 75, Zhengzhou, 450052, China
| | - Yu Zhang
- State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Qianjin Street 2699, Changchun, 130012, China
| | - Chongxin Shan
- Key Laboratory of Materials Physics of Ministry of Education, School of Physics, Zhengzhou University, Daxue Road 75, Zhengzhou, 450052, China
| | - Zhifeng Shi
- Key Laboratory of Materials Physics of Ministry of Education, School of Physics, Zhengzhou University, Daxue Road 75, Zhengzhou, 450052, China
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de Clercq DM, Collins MI, Sloane NP, Feng J, McCamey DR, Tayebjee MJY, Nielsen MP, Schmidt TW. Singlet fission in TIPS-anthracene thin films. Chem Sci 2024; 15:6402-6409. [PMID: 38699250 PMCID: PMC11062091 DOI: 10.1039/d3sc06774b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2023] [Accepted: 03/24/2024] [Indexed: 05/05/2024] Open
Abstract
Singlet fission is an exciton multiplication process that allows for the conversion of one singlet exciton into two triplet excitons. Organic semiconductors, such as acenes and their soluble bis(triisopropylsilylethynyl) (TIPS) substituted counterparts, have played a major role in elucidating the understanding of the underlying mechanisms of singlet fission. Despite this, one prominent member of the acene family that has received little experimental attention to date is TIPS-anthracene, even with computational studies suggesting potential high singlet fission yields in the solid state. Here, time-resolved spectroscopic and magneto-photoluminescence measurements were performed on spin-cast films of TIPS-anthracene, showing evidence for singlet fission. A singlet fission yield of 19% (out of 200%) is estimated from transient absorption spectroscopy. Kinetic modeling of the magnetic field effect on photoluminescence suggests that fast rates of triplet dissociation lead to a low magnetic photoluminescence effect and that non-radiative decay of both the S1 and 1(TT) states is the cause for the low triplet yield.
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Affiliation(s)
- Damon M de Clercq
- School of Chemistry, ARC Centre of Excellence in Exciton Science, UNSW Sydney NSW 2052 Australia
| | - Miles I Collins
- School of Physics, ARC Centre of Excellence in Exciton Science, UNSW Sydney NSW 2052 Australia
| | - Nicholas P Sloane
- School of Physics, ARC Centre of Excellence in Exciton Science, UNSW Sydney NSW 2052 Australia
| | - Jiale Feng
- School of Chemistry, ARC Centre of Excellence in Exciton Science, UNSW Sydney NSW 2052 Australia
| | - Dane R McCamey
- School of Physics, ARC Centre of Excellence in Exciton Science, UNSW Sydney NSW 2052 Australia
| | - Murad J Y Tayebjee
- School of Photovoltaic and Renewable Energy Engineering, UNSW Sydney NSW 2052 Australia
| | - Michael P Nielsen
- School of Photovoltaic and Renewable Energy Engineering, UNSW Sydney NSW 2052 Australia
| | - Timothy W Schmidt
- School of Chemistry, ARC Centre of Excellence in Exciton Science, UNSW Sydney NSW 2052 Australia
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Li W, Bao X, Wang C, Yao Y, Song J, Peng K, Xu S, Chen L, Guan Y, Niu L. Exploring charge generation and separation in tandem organic light-emitting diodes based on magneto-electroluminescence. NANOTECHNOLOGY 2024; 35:175203. [PMID: 38150721 DOI: 10.1088/1361-6528/ad18e4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/06/2023] [Accepted: 12/27/2023] [Indexed: 12/29/2023]
Abstract
5,6,11,12-tetraphenylnaphthacene (rubrene) exhibits resonant energy properties (ES1,rub≈ 2ET1,rub), resulting in rubrene-based organic light-emitting diode (OLED) devices that undergo the singlet fission (STT) process at room temperature. This unique process gives rise to a distinct magneto-electroluminescence (MEL) profile, differing significantly from the typical intersystem crossing (ISC) process. Therefore, in this paper, we investigate charge generation and separation in the interconnector, and the mechanism of charge transport in tandem OLEDs at room temperature using MEL tools. We fabricate tandem OLEDs comprising green (Alq3) and yellow (Alq3:rubrene) electroluminescence (EL) units using different interconnectors. The results demonstrate that all devices exhibited significant rubrene emission. However, the MEL did not exhibit an STT process with an increasing magnetic field, but rather a triplet-triplet annihilation (TTA) process. This occurrence is attributed to direct carrier trapping within doped EL units, which hinders the transport of rubrene trapped charges, consequently prolonging the lifetime of triplet excitons (T1,rub). Thus, the increased T1,rubconcentration causes TTA to occur at room temperature, causing the rapid decrease of MEL in all devices under high magnetic fields. In devices where only the TTA process occurs, the TTA increases with the increasing current. Consequently, the high magnetic field of devices A-C is only related to TTA. Notably, there exists a high magnetic field TTA of device D in the Alq3/1,4,5,8,9,11-Hexaazatriphenylene-hexacarbonitrile interconnector regardless of the current. This occurs because both EL units in the device emit simultaneously, resulting in the triplet-charge annihilation process of Alq3in the high magnetic field of the MEL. Moreover, the rapid increase in MEL at low magnetic field across all devices is attributed to the ISC between Alq3polaron pairs. This entire process involves Förster and Dexter energy transfer. This article not only provides novel insights into charge generation and separation in the interconnector but also enhances our understanding of the microscopic mechanisms in tandem OLED devices.
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Affiliation(s)
- Wanjiao Li
- Key Laboratory of Optoelectronic Engineering, College of Physics and Electronic Engineering, Chongqing Normal University, Chongqing 401331, People's Republic of China
| | - Xi Bao
- Key Laboratory of Optoelectronic Engineering, College of Physics and Electronic Engineering, Chongqing Normal University, Chongqing 401331, People's Republic of China
| | - Cheng Wang
- Key Laboratory of Optoelectronic Engineering, College of Physics and Electronic Engineering, Chongqing Normal University, Chongqing 401331, People's Republic of China
| | - Yu Yao
- Key Laboratory of Optoelectronic Engineering, College of Physics and Electronic Engineering, Chongqing Normal University, Chongqing 401331, People's Republic of China
| | - Jiayi Song
- Key Laboratory of Optoelectronic Engineering, College of Physics and Electronic Engineering, Chongqing Normal University, Chongqing 401331, People's Republic of China
| | - Keao Peng
- Key Laboratory of Optoelectronic Engineering, College of Physics and Electronic Engineering, Chongqing Normal University, Chongqing 401331, People's Republic of China
| | - Shuang Xu
- Key Laboratory of Optoelectronic Engineering, College of Physics and Electronic Engineering, Chongqing Normal University, Chongqing 401331, People's Republic of China
| | - Lijia Chen
- Key Laboratory of Optoelectronic Engineering, College of Physics and Electronic Engineering, Chongqing Normal University, Chongqing 401331, People's Republic of China
| | - Yunxia Guan
- Key Laboratory of Optoelectronic Engineering, College of Physics and Electronic Engineering, Chongqing Normal University, Chongqing 401331, People's Republic of China
| | - Lianbin Niu
- Key Laboratory of Optoelectronic Engineering, College of Physics and Electronic Engineering, Chongqing Normal University, Chongqing 401331, People's Republic of China
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Song J, Guan Y, Wang C, Bao X, Li W, Peng K, Xu S, Chen L, Niu L. Realizing high efficiency and luminance in green, yellow and blue organic light emitting diode by deoxyribonucleic acid. NANOTECHNOLOGY 2023; 34:505201. [PMID: 37708884 DOI: 10.1088/1361-6528/acf9ae] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/18/2023] [Accepted: 09/14/2023] [Indexed: 09/16/2023]
Abstract
Although the effect of the electron blocking layer (EBL) material, deoxyribonucleic acid (DNA), on the electroluminescence (EL) performance of organic light-emitting diodes (OLEDs) has been studied, the process of DNA regulation of exciton recombination region within the device is still unclear. Herein, devices with and without EBL were fabricated using different DNA spin-coating speeds, and the photoelectric performance of device were measured. By using DNA compounded with cetyltrimethyl ammonium (CTMA) as the EBL and hole buffer layer, so-called BioLEDs. The DNA-based green Alq3BioLEDs achieve higher luminance (39 000 cd m-2) and higher current efficiency (8.4 cd A-1), which are increased by 49% and 54%, respectively, compared to the reference OLEDs without the addition of DNA. Similarly, the maximum luminance and efficiency of yellow Rubrene BioLEDs is increased by 64% (from 12 120 to 19 820 cd m-2) and 74% (from 1.36 to 2.36 cd A-1), the luminance and efficiency of blue TCTA BioLEDs is increased by 101% and 245%. Specifically, we found that as the thickness of DNA-CTMA increases, the exciton recombination region moves towards the interface between the emitting layer (EML) and the hole transport layer (HTL). By better confining excitons within the EML, the current efficiency of the BioLEDs is effectively improved. Accordingly, we provide a possible idea for achieve high performance DNA-based BioLEDs by adding DNA-CTMA EBL and hole buffer layers. Meanwhile, as the DNA thickness increases, the exciton recombination region moves towards the EML/HTL interface, thereby enhancing the efficiency of the DNA-based BioLEDs.
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Affiliation(s)
- Jiayi Song
- Key Laboratory of Optical Engineering, College of Physics and Electronic Engineering, Chongqing Normal University, Chongqing, 401331, People's Republic of China
| | - Yunxia Guan
- Key Laboratory of Optical Engineering, College of Physics and Electronic Engineering, Chongqing Normal University, Chongqing, 401331, People's Republic of China
| | - Cheng Wang
- Key Laboratory of Optical Engineering, College of Physics and Electronic Engineering, Chongqing Normal University, Chongqing, 401331, People's Republic of China
| | - Xi Bao
- Key Laboratory of Optical Engineering, College of Physics and Electronic Engineering, Chongqing Normal University, Chongqing, 401331, People's Republic of China
| | - Wanjiao Li
- Key Laboratory of Optical Engineering, College of Physics and Electronic Engineering, Chongqing Normal University, Chongqing, 401331, People's Republic of China
| | - Keao Peng
- Key Laboratory of Optical Engineering, College of Physics and Electronic Engineering, Chongqing Normal University, Chongqing, 401331, People's Republic of China
| | - Shuang Xu
- Key Laboratory of Optical Engineering, College of Physics and Electronic Engineering, Chongqing Normal University, Chongqing, 401331, People's Republic of China
| | - Lijia Chen
- Key Laboratory of Optical Engineering, College of Physics and Electronic Engineering, Chongqing Normal University, Chongqing, 401331, People's Republic of China
| | - Lianbin Niu
- Key Laboratory of Optical Engineering, College of Physics and Electronic Engineering, Chongqing Normal University, Chongqing, 401331, People's Republic of China
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Song J, Guan Y, Wang C, Bao X, Li W, Chen L, Niu L. Investigations on exciton recombination and annihilation in TmPyPB-ETL OLEDs using magnetic field effects. Phys Chem Chem Phys 2023; 25:23783-23791. [PMID: 37622246 DOI: 10.1039/d3cp02332j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/26/2023]
Abstract
Although the effect of the electron transport layer (ETL) material TmPyPb on the electroluminescence performance of organic light-emitting diodes (OLEDs) has been extensively studied, the process of TmPyPb regulating exciton recombination and annihilation within the device is still unclear. Here, we fabricated devices of various TmPyPb thicknesses with and without ETL. Subsequently, we measured the magneto-electroluminescence (MEL) of these devices. Specifically, at the same luminance, the triplet-charge annihilation (TQA) process is more likely to occur as the thickness of TmPyPb increases, resulting in a decrease in the maximum luminance of devices. Due to electron leakage and exciton recombination region moving towards the cathode, leading to a decrease in luminance efficiency at first and then an enhancement with an increase in the thickness of TmPyPb. Furthermore, at room temperature, the application of a large bias voltage suppresses singlet fission (SF) processes by modulating the dissociation of singlet polaron pairs (PPS) and the concentration of triplet exciton (T1). This leads to the conversion of SF to the TQA process. At low temperatures, the bias voltage and temperature can regulate the concentration and lifetime of PPS and T1. Therefore, as the temperature decreases, the transition of SF → TQA → triplet-triplet annihilation (TTA) and TQA coexistence → TTA process occurs. Moreover, MEL responses of the TmPyPb-ETL device show a W-linear pattern owing to the combined effect of the hyperfine interaction (HFI) and Zeeman splitting at 145 K. Accordingly, we explored the electroluminescence (EL) performance of TmPyPB-ETL OLEDs and investigated the evolution of SF, TQA, and TTA processes using MEL. Our study revealed the effect of exciton recombination and annihilation in OLEDs with varying thicknesses of TmPyPb.
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Affiliation(s)
- Jiayi Song
- College of Physics and Electronic Engineering, Chongqing Normal University, Chongqing, 401331, People's Republic of China.
| | - Yunxia Guan
- College of Physics and Electronic Engineering, Chongqing Normal University, Chongqing, 401331, People's Republic of China.
| | - Cheng Wang
- College of Physics and Electronic Engineering, Chongqing Normal University, Chongqing, 401331, People's Republic of China.
| | - Xi Bao
- College of Physics and Electronic Engineering, Chongqing Normal University, Chongqing, 401331, People's Republic of China.
| | - Wanjiao Li
- College of Physics and Electronic Engineering, Chongqing Normal University, Chongqing, 401331, People's Republic of China.
| | - Lijia Chen
- College of Physics and Electronic Engineering, Chongqing Normal University, Chongqing, 401331, People's Republic of China.
| | - Lianbin Niu
- College of Physics and Electronic Engineering, Chongqing Normal University, Chongqing, 401331, People's Republic of China.
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Park SW, Kim D, Rhee YM. Overcoming the Limitation of Spin Statistics in Organic Light Emitting Diodes (OLEDs): Hot Exciton Mechanism and Its Characterization. Int J Mol Sci 2023; 24:12362. [PMID: 37569740 PMCID: PMC10418923 DOI: 10.3390/ijms241512362] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2023] [Revised: 07/28/2023] [Accepted: 07/31/2023] [Indexed: 08/13/2023] Open
Abstract
Triplet harvesting processes are essential for enhancing efficiencies of fluorescent organic light-emitting diodes. Besides more conventional thermally activated delayed fluorescence and triplet-triplet annihilation, the hot exciton mechanism has been recently noticed because it helps reduce the efficiency roll-off and improve device stability. Hot exciton materials enable the conversion of triplet excitons to singlet ones via reverse inter-system crossing from high-lying triplet states and thereby the depopulation of long-lived triplet excitons that are prone to chemical and/or efficiency degradation. Although their anti-Kasha characteristics have not been clearly explained, numerous molecules with behaviors assigned to the hot exciton mechanism have been reported. Indeed, the related developments appear to have just passed the stage of infancy now, and there will likely be more roles that computational elucidations can play. With this perspective in mind, we review some selected experimental studies on the mechanism and the related designs and then on computational studies. On the computational side, we examine what has been found and what is still missing with regard to properly understanding this interesting mechanism. We further discuss potential future points of computational interests toward aiming for eventually presenting in silico design guides.
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Affiliation(s)
- Soo Wan Park
- Department of Chemistry, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Republic of Korea
| | - Dongwook Kim
- Department of Chemistry, Kyonggi University, Suwon 16227, Republic of Korea
| | - Young Min Rhee
- Department of Chemistry, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Republic of Korea
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Sun Q, Wu Y, Cui Y, Gao C, Ou Q, Hu D, Wang L, Wang Y, Dong H, Zhao J, Zhang C, Shuai Z, Fu H, Peng Q. Molecular design of DBA-type five-membered heterocyclic rings to achieve 200% exciton utilization for electroluminescence. MATERIALS HORIZONS 2022; 9:2518-2523. [PMID: 36125332 DOI: 10.1039/d2mh00919f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Achieving high exciton utilization is a long-cherished goal in the development of organic light-emitting diode materials. Herein, a three-step mechanism is proposed to achieve 200% exciton utilization: (i) hot triplet exciton (T2) conversion to singlet S1; (ii) singlet fission from S1 into two T1; (iii) and then a Dexter energy transfer to phosphors. The requirement is that S1 should lie slightly lower than or close to T2 and twice as high as T1 in energy. For this, a scenario is put forward to design a series of donor-bridge-acceptor (DBA) type molecules with 2E(T1) ≤ E(S1) < E(T2), in which the Baird-type aromatic pyrazoline ring is used as a bridge owing to its stabilized T1 (1.30-1.74 eV) and different kinds of donors and acceptors are linked to the bridge for regulating S1 (2.35-3.87 eV) and T2 (2.44-3.96 eV). The ultrafast spectroscopy and sensitization measurements for one compound (TPA-DBPrz) fully confirm the theoretical predictions.
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Affiliation(s)
- Qi Sun
- MOE Key Laboratory of Organic Optoelectronics and Molecular Engineering, Department of Chemistry, Tsinghua University, Beijing, 100084, P. R. China.
| | - Yishi Wu
- Department of Chemistry, Capital Normal University, Beijing 100048, P. R. China
| | - Yuanyuan Cui
- College of Chemistry, Jilin University, Changchun 130012, P. R. China
| | - Can Gao
- Institute of chemistry, Chinese Academy of Sciences, Beijing, 100049, P. R. China
| | - Qi Ou
- MOE Key Laboratory of Organic Optoelectronics and Molecular Engineering, Department of Chemistry, Tsinghua University, Beijing, 100084, P. R. China.
| | - Deping Hu
- MOE Key Laboratory of Organic Optoelectronics and Molecular Engineering, Department of Chemistry, Tsinghua University, Beijing, 100084, P. R. China.
| | - Lu Wang
- MOE Key Laboratory of Organic Optoelectronics and Molecular Engineering, Department of Chemistry, Tsinghua University, Beijing, 100084, P. R. China.
| | - Yue Wang
- College of Chemistry, Jilin University, Changchun 130012, P. R. China
| | - Huanli Dong
- Institute of chemistry, Chinese Academy of Sciences, Beijing, 100049, P. R. China
| | - Jianzhang Zhao
- School of Chemical Engineering, Dalian University of Technology, 2 Ling Gong Road, Dalian 116024, P. R. China
| | - Chunfeng Zhang
- School of Physics, Nanjing University, Nanjing, 210093, China
| | - Zhigang Shuai
- MOE Key Laboratory of Organic Optoelectronics and Molecular Engineering, Department of Chemistry, Tsinghua University, Beijing, 100084, P. R. China.
| | - Hongbing Fu
- Department of Chemistry, Capital Normal University, Beijing 100048, P. R. China
| | - Qian Peng
- School of Chemical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, P. R. China.
- Institute of chemistry, Chinese Academy of Sciences, Beijing, 100049, P. R. China
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Baronas P, Kreiza G, Naimovičius L, Radiunas E, Kazlauskas K, Orentas E, Juršėnas S. Sweet Spot of Intermolecular Coupling in Crystalline Rubrene: Intermolecular Separation to Minimize Singlet Fission and Retain Triplet-Triplet Annihilation. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2022; 126:15327-15335. [PMID: 36147521 PMCID: PMC9484276 DOI: 10.1021/acs.jpcc.2c04572] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2022] [Revised: 08/16/2022] [Indexed: 06/15/2023]
Abstract
Singlet fission is detrimental to NIR-to-vis photon upconversion in the solid rubrene (Rub) films, as it diminishes photoluminescence efficiency. Previous studies have shown that thermally activated triplet energy transport drives singlet fission with nearly 100% efficiency in closely packed Rub crystals. Here, we examine triplet separation and recombination as a function of intermolecular distance in the crystalline films of Rub and the t-butyl substituted rubrene (tBRub) derivative. The increased intermolecular distance and altered molecular packing in tBRub films cause suppressed singlet dissociation into free triplets due to slower triplet energy transport. It was found that the formation of correlated triplet pairs 1(TT) and partial triplet separation 1(T···T) occurs in both Rub and tBRub films despite differences in intermolecular coupling. Under weak intermolecular coupling as in tBRub, geminate triplet annihilation of 1(T···T) outcompetes dissociation into free triplets, resulting in emission from the 1(TT) state. Essentially, increasing intermolecular distance up to a certain point (a sweet spot) is a good strategy for suppressing singlet fission and retaining triplet-triplet annihilation properties.
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Affiliation(s)
- P. Baronas
- Institute
of Photonics and Nanotechnology, Vilnius
University, Sauletekio 3, LT-10257 Vilnius, Lithuania
| | - G. Kreiza
- Institute
of Photonics and Nanotechnology, Vilnius
University, Sauletekio 3, LT-10257 Vilnius, Lithuania
| | - L. Naimovičius
- Institute
of Photonics and Nanotechnology, Vilnius
University, Sauletekio 3, LT-10257 Vilnius, Lithuania
| | - E. Radiunas
- Institute
of Photonics and Nanotechnology, Vilnius
University, Sauletekio 3, LT-10257 Vilnius, Lithuania
| | - K. Kazlauskas
- Institute
of Photonics and Nanotechnology, Vilnius
University, Sauletekio 3, LT-10257 Vilnius, Lithuania
| | - E. Orentas
- Institute
of Chemistry, Faculty of Chemistry and Geosciences, Vilnius University, Naugarduko 24, LT-03225 Vilnius, Lithuania
| | - S. Juršėnas
- Institute
of Photonics and Nanotechnology, Vilnius
University, Sauletekio 3, LT-10257 Vilnius, Lithuania
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11
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Wang Y, Guo Z, Gao Y, Tian Y, Deng Y, Ma X, Yang W. Tuning Hybridized Local and Charge-Transfer Mixing for Efficient Hot-Exciton Emission with Improved Color Purity. J Phys Chem Lett 2022; 13:6664-6673. [PMID: 35839081 DOI: 10.1021/acs.jpclett.2c01917] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Delayed fluorescence (DF) emitters with high color purity are of high interest for applications in high-resolution displays. However, the charge transfer required by high emitting efficiency usually conflicts with the expected color purity. In this work, we investigated the S1/S0 conformational relaxation, spin-orbital coupling (SOC), and vibronic coupling of hot-exciton emitters while hybrid local and charge transfer (HLCT) state tuning was achieved by a structural meta-effect. The meta-linkage leads to suppressed S1/S0 conformational relaxation and weakened vibronic coupling, while the unsacrificed emitting efficiency is largely ensured by multiple rISC channels (Tn → Sm) with thermally accessible triplet-singlet energy gap (ΔEST) and effective SOC. We demonstrated that the unique excited-state mechanism provides opportunities to improve the emitting color purity of hot-exciton emitters without sacrificing emitting efficiency by HLCT state tuning with simple chemical structural modification, for which hot-exciton emitters might play a more important role for high-resolution organic light-emitting diode displays.
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Affiliation(s)
- Yaxin Wang
- Institute of Molecular Plus, Tianjin University, Tianjin 300072, P.R. China
| | - Zilong Guo
- Institute of Molecular Plus, Tianjin University, Tianjin 300072, P.R. China
| | - Yixuan Gao
- Institute of Molecular Plus, Tianjin University, Tianjin 300072, P.R. China
| | - Yiran Tian
- Institute of Molecular Plus, Tianjin University, Tianjin 300072, P.R. China
| | - Yingyi Deng
- Institute of Molecular Plus, Tianjin University, Tianjin 300072, P.R. China
| | - Xiaonan Ma
- Institute of Molecular Plus, Tianjin University, Tianjin 300072, P.R. China
| | - Wensheng Yang
- Institute of Molecular Plus, Tianjin University, Tianjin 300072, P.R. China
- Engineering Research Center for Nanomaterials, Henan University, Kaifeng 475004, P.R. China
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12
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Bossanyi DG, Sasaki Y, Wang S, Chekulaev D, Kimizuka N, Yanai N, Clark J. Spin Statistics for Triplet-Triplet Annihilation Upconversion: Exchange Coupling, Intermolecular Orientation, and Reverse Intersystem Crossing. JACS AU 2021; 1:2188-2201. [PMID: 34977890 PMCID: PMC8715495 DOI: 10.1021/jacsau.1c00322] [Citation(s) in RCA: 49] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/21/2021] [Indexed: 06/14/2023]
Abstract
Triplet-triplet annihilation upconversion (TTA-UC) has great potential to significantly improve the light harvesting capabilities of photovoltaic cells and is also sought after for biomedical applications. Many factors combine to influence the overall efficiency of TTA-UC, the most fundamental of which is the spin statistical factor, η, that gives the probability that a bright singlet state is formed from a pair of annihilating triplet states. The value of η is also critical in determining the contribution of TTA to the overall efficiency of organic light-emitting diodes. Using solid rubrene as a model system, we reiterate why experimentally measured magnetic field effects prove that annihilating triplets first form weakly exchange-coupled triplet-pair states. This is contrary to conventional discussions of TTA-UC that implicitly assume strong exchange coupling, and we show that it has profound implications for the spin statistical factor η. For example, variations in intermolecular orientation tune η from to through spin mixing of the triplet-pair wave functions. Because the fate of spin-1 triplet-pair states is particularly crucial in determining η, we investigate it in rubrene using pump-push-probe spectroscopy and find additional evidence for the recently reported high-level reverse intersystem crossing channel. We incorporate all of these factors into an updated model framework with which to understand the spin statistics of TTA-UC and use it to rationalize the differences in reported values of η among different common annihilator systems. We suggest that harnessing high-level reverse intersystem crossing channels in new annihilator molecules may be a highly promising strategy to exceed any spin statistical limit.
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Affiliation(s)
- David G. Bossanyi
- Department
of Physics and Astronomy, The University
of Sheffield, Hicks Building, Hounsfield Road, Sheffield S3 7RH, U.K.
| | - Yoichi Sasaki
- Department
of Chemistry and Biochemistry, Graduate School of Engineering, Center
for Molecular Systems (CMS), Kyushu University, 744 Moto-oka, Nishi-ku, Fukuoka 819-0395, Japan
| | - Shuangqing Wang
- Department
of Physics and Astronomy, The University
of Sheffield, Hicks Building, Hounsfield Road, Sheffield S3 7RH, U.K.
| | - Dimitri Chekulaev
- Department
of Chemistry, The University of Sheffield, Dainton Building, Brook Hill, Sheffield S3 7HF, U.K.
| | - Nobuo Kimizuka
- Department
of Chemistry and Biochemistry, Graduate School of Engineering, Center
for Molecular Systems (CMS), Kyushu University, 744 Moto-oka, Nishi-ku, Fukuoka 819-0395, Japan
| | - Nobuhiro Yanai
- Department
of Chemistry and Biochemistry, Graduate School of Engineering, Center
for Molecular Systems (CMS), Kyushu University, 744 Moto-oka, Nishi-ku, Fukuoka 819-0395, Japan
| | - Jenny Clark
- Department
of Physics and Astronomy, The University
of Sheffield, Hicks Building, Hounsfield Road, Sheffield S3 7RH, U.K.
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13
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Krueger TD, Fang C. Elucidating Inner Workings of Naturally Sourced Organic Optoelectronic Materials with Ultrafast Spectroscopy. Chemistry 2021; 27:17736-17750. [PMID: 34545971 DOI: 10.1002/chem.202102766] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2021] [Indexed: 01/18/2023]
Abstract
Recent advances in sustainable optoelectronics including photovoltaics, light-emitting diodes, transistors, and semiconductors have been enabled by π-conjugated organic molecules. A fundamental understanding of light-matter interactions involving these materials can be realized by time-resolved electronic and vibrational spectroscopies. In this Minireview, the photoinduced mechanisms including charge/energy transfer, electronic (de)localization, and excited-state proton transfer are correlated with functional properties encompassing optical absorption, fluorescence quantum yield, conductivity, and photostability. Four naturally derived molecules (xylindein, dimethylxylindein, alizarin, indigo) with ultrafast spectral insights showcase efficient energy dissipation involving H-bonding networks and proton motions, which yield high photostability. Rational design principles derived from such investigations could increase the efficiency for light harvesting, triplet formation, and photosensitivity for improved and versatile optoelectronic performance.
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Affiliation(s)
- Taylor D Krueger
- Department of Chemistry, Oregon State University, 153 Gilbert Hall, Corvallis, OR, 97331-4003, USA
| | - Chong Fang
- Department of Chemistry, Oregon State University, 153 Gilbert Hall, Corvallis, OR, 97331-4003, USA
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14
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Dettmann MA, Cavalcante LSR, Magdaleno C, Masalkovaitė K, Vong D, Dull JT, Rand BP, Daemen LL, Goldman N, Faller R, Moulé AJ. Comparing the Expense and Accuracy of Methods to Simulate Atomic Vibrations in Rubrene. J Chem Theory Comput 2021; 17:7313-7320. [PMID: 34818006 DOI: 10.1021/acs.jctc.1c00747] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Atomic vibrations can inform about materials properties from hole transport in organic semiconductors to correlated disorder in metal-organic frameworks. Currently, there are several methods for predicting these vibrations using simulations, but the accuracy-efficiency tradeoffs have not been examined in depth. In this study, rubrene is used as a model system to predict atomic vibrational properties using six different simulation methods: density functional theory, density functional tight binding, density functional tight binding with a Chebyshev polynomial-based correction, a trained machine learning model, a pretrained machine learning model called ANI-1, and a classical forcefield model. The accuracy of each method is evaluated by comparison to the experimental inelastic neutron scattering spectrum. All methods discussed here show some accuracy across a wide energy region, though the Chebyshev-corrected tight-binding method showed the optimal combination of high accuracy with low expense. We then offer broad simulation guidelines to yield efficient, accurate results for inelastic neutron scattering spectrum prediction.
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Affiliation(s)
- Makena A Dettmann
- University of California Davis, Davis, California 95616, United States
| | | | - Corina Magdaleno
- University of California Davis, Davis, California 95616, United States
| | | | - Daniel Vong
- University of California Davis, Davis, California 95616, United States
| | - Jordan T Dull
- Department of Electrical Engineering, Princeton University, Princeton, New Jersey 08544, United States
| | - Barry P Rand
- Department of Electrical Engineering, Princeton University, Princeton, New Jersey 08544, United States
| | - Luke L Daemen
- Oak Ridge National Lab, Oak Ridge, Tennessee 37831, United States
| | - Nir Goldman
- University of California Davis, Davis, California 95616, United States.,Lawrence Livermore National Lab, Livermore, California 94550, United States
| | - Roland Faller
- University of California Davis, Davis, California 95616, United States
| | - Adam J Moulé
- University of California Davis, Davis, California 95616, United States
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15
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Xu Y, Xu P, Hu D, Ma Y. Recent progress in hot exciton materials for organic light-emitting diodes. Chem Soc Rev 2020; 50:1030-1069. [PMID: 33231588 DOI: 10.1039/d0cs00391c] [Citation(s) in RCA: 190] [Impact Index Per Article: 38.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
According to Kasha's rule, high-lying excited states usually have little effect on fluorescence. However, in some molecular systems, the high-lying excited states partly or even mainly contribute to the photophysical properties, especially in the process of harvesting triplet excitons in organic electroluminescent devices. In the current review, we focus on a type of organic light-emitting diode (OLED) materials called "hot exciton" materials, which can effectively harness the non-radiative triplet excitons via reverse intersystem crossing (RISC) from high-lying triplet states to singlet states (Tn→ Sm; n≥ 2, m≥ 1). Since Ma and Yang proposed the hot exciton mechanism for OLED material design in 2012, there have been many reports aiming at the design and synthesis of novel hot exciton luminogens. Herein, we present a comprehensive review of the recent progress in hot exciton materials. The developments of the hot exciton mechanism are reviewed, the fundamental principles regarding molecular design are discussed, and representative reported hot exciton luminogens are summarized and analyzed, along with their structure-property relationships and OLED applications.
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Affiliation(s)
- Yuwei Xu
- Institute of Polymer Optoelectronic Materials and Devices, State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou 510640, P. R. China.
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