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Simultaneous and Significant Improvements in Efficiency and Stability of Deep‐Blue Organic Light Emitting Diodes through Friedel‐Crafts Arylmethylation of a Fluorophore
Author(s) -
Feng Quanyou,
Tan Kesheng,
Zheng Xiaojun,
Xie Songlin,
Xue Kai,
Bo Yifan,
Zhang He,
Lin Dongqing,
Rao Junfeng,
Xie Xinmiao,
Xie Linghai,
Cao Hongtao,
Zhang Hongmei,
Wei Ying,
Huang Wei
Publication year - 2020
Publication title -
chemphotochem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.13
H-Index - 18
ISSN - 2367-0932
DOI - 10.1002/cptc.201900268
Subject(s) - oled , electroluminescence , quantum efficiency , full width at half maximum , optoelectronics , common emitter , materials science , carbazole , brightness , luminance , fluorescence , diode , deep blue , fluorophore , photochemistry , chemistry , optics , physics , nanotechnology , layer (electronics)
The molecular design of purely organic fluorophores for highly efficient and stable deep‐blue organic light‐emitting diodes (OLEDs) is still a challenge. Excellent performances in terms of Commission Internationale de l'Eclairage (CIE) coordinates, external quantum efficiency (EQE), brightness and lifespan, often cannot be achieved simultaneously in one deep‐blue OLED. Herein, a novel carbazole‐based thermally activated delayed fluorescence emitter DPFCz ‐ TRZ is designed and synthesized through Friedel‐Crafts arylmethylation of Cz ‐ TRZ . Compared with the parent compound Cz ‐ TRZ , the OLED based on DPFCz ‐ TRZ exhibits significantly improved performances with a maximum EQE of 15.5 % and brightness beyond 16000 cd m −2 , while retaining similar deep‐blue emission with a CIE coordinate of (0.15, 0.10), an electroluminescence (EL) maximum of λ =445 nm and full width at half maximum (FWHM) of 65 nm. Additionally, the device also shows a respectable lifetime (LT50, time to 50 % of initial luminance) of 78 h at 500 cd m −2 , corresponding to a LT50 of 1304 h at 100 cd m −2 . Impressively, a record high EQE of 5.2 % can be obtained at a very high luminance of 10000 cd m −2 . This work demonstrates the first report of simultaneous achievement over 15 % EQE and 1000 h LT50 (100 cd m −2 ) in deep‐blue purely organic electroluminescence devices with a coordinate of (≤0.15, ≤0.10) and maximum brightness beyond 16000 cd m −2 .