Ambipolar Phosphine Derivatives to Attain True Blue OLEDs with 6.5% EQE

Efficient blue electroluminescence with an external quantum efficiency of 9.20% and CIE y < 0.08 without excimer emission

Aromatically substituted phenanthroimidazoles at the C6 and C9 positions enhanced the thermal, photochemical and electroluminescence properties due to extension of conjugation. These new materials exhibit good photophysical properties with high thermal stability, good film-forming property and high luminous efficiency. The electroluminescence performances of C6 and C9 modified phenanthroimidazoles as host emitters were evaluated as well as the dopant in the fabricated devices. Among the non-doped devices, pyrene substituted PPI-Py or PPICN-Py based devices show maximum efficiency: PPI-Py/PPICN-Py: η c (cd A-1) - 9.20/9.98; η p (lm W-1) - 8.50/9.16; η ex (%) - 5.56/5.80. The doped OLEDs, m-MTDATA/TAPC:PPI-Cz (4.81/4.85%), m-MTDATA/TAPC:PPICN-Cz (5.23/5.26%), m-MTDATA/TAPC:PPI-An (5.01/5.04%), m-MTDATA/TAPC:PPICN-An (5.25/5.28%), m-MTDATA/TAPC:PPI-Py (5.61/5.65%) and m-MTDATA/TAPC:PPICN-Py (5.76/5.78%) show improved device efficiencies compared to non-doped devices. Designing C6/C9 modified phenanthrimidazole fluorophores is an efficient strategy for constructing highly efficient OLEDs.

Solvatochromic dual luminescence of Eu–Au dyads decorated with chromophore phosphines

Chromophore-containing phosphines produce highly solvatochromic gold(i) fluorophores. Their combination with red-emitting Eu centers offers a facile approach to dual emissive complexes with widely tunable luminescence characteristics.

Spirally Configured ( cis-Stilbene) Trimers: Steady-State and Time-Resolved Photophysical Studies and Organic Light-Emitting Diode Applications

This article reports for the time-resolved photophysical studies of spirally configured ( cis-stilbene) trimers and their spin-coated organic light-emitting diode (OLED) device performances. Transient absorption profiles of spirally configured, ter-( cis-stilbene) were studied by pulse radiolysis. The emission profiles after charge recombination of their incipient radical ions in benzene provides insights into the emission mechanism and efficiency in OLED devices. Blue-, sky blue-, and green-emitting OLED devices for a maximum external quantum efficiency are 4.32%, 4.70%, and 2.77%, respectively, by solution process.

EQE Climbing Over 6% at High Brightness of 14350 cd/m2 in Deep-Blue OLEDs Based on Hybridized Local and Charge-Transfer Fluorescence

Three deep-blue emitters PPi-Pid, PPi-Xid, and PPi-Mid based on a novel conjugated system phenantroimidazole-π-indolizine have been designed and synthesized. Here, indolizine with appropriate π-conjugation length was used as the acceptor profited from its high-photoluminescence quantum yield and good electron-withdrawing ability. Fluorescent organic light-emitting diodes (OLEDs) based on PPi-Pid, PPi-Xid, and PPi-Mid achieved deep-blue emissions with the Commission Internationale de L'Eclairage coordinates of (0.151, 0.076), (0.155, 0.052), and (0.153, 0.052); high brightness of 14350, 4377, and 4002 cd/m²; and high external quantum efficiencies (EQEs) of 6.01, 3.90, and 4.28%, respectively. Moreover, it is noticeable that all of the devices exhibited efficiencies increasing with brightness. In particular, the PPi-Pid-based device exhibited high EQE over 6% at a high brightness of 14350 cd/m². Such high brightness along with high EQE is very rare whether in deep-blue fluorescent or thermally activated delayed fluorescent OLEDs.

Aromatically C6- and C9-Substituted Phenanthro[9,10-d]imidazole Blue Fluorophores: Structure-Property Relationship and Electroluminescent Application

In this study, a series of aromatically substituted phenanthro[9,10-d]imidazole (PI) fluorophores at C6 and C9 (no. 6 and 9 carbon atoms) have been synthesized and systematically characterized by theoretical, thermal, photophysical, electrochemical, and electroluminescent (EL) studies. C6 and C9 modifications have positive influences on the thermal properties of the new materials. Theoretical calculations suggest that the C6 and the C9 positions of PI are electronically different. Theoretical and experimental evidences of intramolecular charge transfer (ICT) between two identical moieties attaching to the C6 and the C9 positions are observed. Photophysical properties of the fluorophores are greatly influenced by size and conjugation extent of the substituents as well as linking steric hindrance. It is found that the C6 and C9 positions afford moderate conjugated extension compared to the C2 modification. Moreover, ICT characteristics of the new fluorophores increase as the size of the substituted aromatic group, and are partially influenced by steric hindrance, with the anthracene and the pyrene derivatives having the strongest ICT excited properties. EL performances of the fluorophores were evaluated as host emitters or dopants in organic light-emitting devices (OLEDs). Most of the devices showed significantly improved efficiencies compared to the OLED using the nonmodified emitter. Among all the devices, a 5 wt % TPI-Py doped device exhibited excellent performances with an external quantum efficiency >5% at 1000 cd/m² and a deep-blue color index of (0.155, 0.065), which are comparable to the most advanced deep-blue devices. Our study can give useful information for designing C6/C9-modificated PI fluorophores and provide an efficient approach for constructing high-performance deep-blue OLEDs.

Achieving efficient violet-blue electroluminescence with CIE y <0.06 and EQE >6% from naphthyl-linked phenanthroimidazole-carbazole hybrid fluorophores

Naphthyl-linked donor–π–acceptor fluorophores were utilized to achieve high performance and good color purity violet-blue emission in organic light-emitting devices (OLEDs).

In this work, we revealed a new approach for the development of efficient violet-blue emitting materials featuring a hybrid local and charge transfer (HLCT) excited state through the incorporation of naphthyl group(s) as a weak n-type π spacer in a donor–π–acceptor (D–π–A) system. The resulting materials (TPINCz and TPIBNCz) show improved intramolecular charge transfer properties and highly efficient violet-blue fluorescence. It is demonstrated that the pattern of the π spacers has significant influence on the photophysical properties. The incorporation of a naphthyl/binaphthyl spacer between the donor and acceptor moieties can alleviate the common dilemma that enhancing device performance by increasing the charge transfer excited properties often leads to red-shifted emissions. A device using TPINCz as an emissive dopant shows a violet-blue emission with CIE coordinates of (0.153, 0.059) and a record high EQE of 6.56 ± 0.11% at a brightness of 1000 cd m^–2. To the best of our knowledge, this performance is the highest among the reported devices with CIE_y ≤0.08. Our study provides a new pathway for the design of high-performance violet-blue emitters with a D–π–A architecture in organic electroluminescence applications.

Dibenzothiophene-platinated complexes: probing the effect of ancillary ligands on the photophysical performance

Alteration of the ancillary mono- and bidentate ligands was used to influence the photoemission behaviour of a family of cyclometalated platinum complexes.

Synthesis and optical and electrochemical properties of julolidine-structured pyrido[3,4-b]indole dye

The julolidine-structured pyrido[3,4-b]indole dye ET-1 possesses the ability to act as a calorimetric and fluorescent sensor for Brønsted and Lewis acids.

Copper-mediated phospha-annulation to attain water-soluble polycyclic luminophores

The P-heterocyclic fluorophores, obtained via Cu(ii)-mediated cyclization, are suitable for cell imaging due to their stability, water solubility and low toxicity.