Ultra‐Deep‐Blue Aggregation‐Induced Delayed Fluorescence Emitters: Achieving Nearly 16% EQE in Solution‐Processed Nondoped and Doped OLEDs with CIE_y < 0.1

Abstract

Ultra‐deep‐blue aggregation‐induced delayed fluorescence (AIDF) emitters (TB‐tCz and TB‐tPCz) bearing organoboron‐based cores as acceptors and 3,6‐substituted carbazoles as donors are presented. The thermally activated delayed fluorescence (TADF) properties of the two emitters are confirmed by theoretical calculations and time‐resolved photoluminescence experiments. TB‐tCz and TB‐tPCz exhibit fast reverse intersystem crossing rate constants owing to efficient spin–orbit coupling between the singlet and triplet states. When applied in solution‐processed organic light‐emitting diodes (OLEDs), the TB‐tCz‐ and TB‐tPCz‐based nondoped devices exhibit ultra‐deep‐blue emissions of 416–428 nm and high color purity owing to their narrow bandwidths of 42.2–44.4 nm, corresponding to the Commission International de l´Eclairage color coordinates of (x = 0.16–0.17, y = 0.05–0.06). They show a maximum external quantum efficiency (EQEmax) of 8.21% and 15.8%, respectively, exhibiting an unprecedented high performance in solution‐processed deep‐blue TADF‐OLEDs. Furthermore, both emitters exhibit excellent device performances (EQEmax = 14.1–15.9%) and color purity in solution‐processed doped OLEDs. The current study provides an AIDF emitter design strategy to implement high‐efficiency deep‐blue OLEDs in the future.

A gold(iii)–TADF emitter as a sensitizer for high-color-purity and efficient deep-blue solution-processed OLEDs

“…7. 5,9,11,12,14,15 The preliminary lifetime of the device with 10 wt% Au-1 and 0.5 wt% ν -DABNA was measured under our laboratory conditions. As shown in Fig.…”

“…1–4 However, compared to green and red ones, the development of blue-emitting materials simultaneously possessing high efficiency and color purity is lagging behind, particularly for low-cost solution-processed OLEDs (SP-OLEDs) that require emissive dopants to be highly soluble in common solvents. 5–16 Wang, Shao, and co-workers recently developed through-space charge transfer polymers containing face-to-face aligned donors and acceptors for achieving efficient blue thermally activated delayed fluorescence (TADF) emission. 6 The SP-OLEDs made with these polymers exhibited high maximum external quantum efficiency (EQE max ) of 18.8%.…”

“…These workers reported another ultra-deep-blue SP-OLED with improved EQE max of 15.8% and CIE coordinates of (0.16, 0.05) relative to their previous results. 12…”

Deep-red electro-fluorescence based on an excimer emission with hot-exciton channels

“…These values are seemingly smaller than those of the metallic complexes or some room-temperature-phosphorescent organic materials that contain heavy atoms, but they can also afford efficient RISC according to the reported studies. 41–45 More importantly, the DMAC-NZC dimer can well inherit both the “hot-exciton” energy structure and the characteristic NTO of its monomer, which is identical to its boosting EUE of the non-doped OLED.…”

New aggregation-induced delayed fluorescent materials for efficient OLEDs with high stabilities of emission color and efficiency

“…[46][47][48][49][50] Actually, OLEDs based on AIDF luminogens have presented excellent EL performances in nondoped and doped devices, comparable to conventional TADF materials but with noticeably enhanced efficiency stability. [51][52][53][54][55][56][57][58] So, in this work, we wish to report two novel AIDF luminogens CDBP-BP-PXZ and CDBP-BP-DMAC, constructed using electron-donors of 9,9 0 -(2,2 0 -dimethyl-[1,1 0 -biphenyl]-4,4 0 -diyl) bis(9H-carbazole) (CDBP) and phenoxazine (PXZ)/9,9-dimethyl-9,10-dihydroacridine (DMAC) and an electron-acceptor of the benzoyl group. The carbonyl therein can achieve effective n-p* transition, which is important to enlarge the spin-orbit coupling (SOC) to facilitate intersystem crossing (ISC) and RISC processes.…”