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A Series of Imidazo[1,2‐f]phenanthridine‐Based Sky‐Blue TADF Emitters Realizing EQE of over 20%
Author(s) -
Ohsawa Tatsuya,
Sasabe Hisahiro,
Watanabe Taiki,
Nakao Kohei,
Komatsu Ryutaro,
Hayashi Yuya,
Hayasaka Yuya,
Kido Junji
Publication year - 2019
Publication title -
advanced optical materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.89
H-Index - 91
ISSN - 2195-1071
DOI - 10.1002/adom.201801282
Subject(s) - phenanthridine , oled , imidazole , materials science , fluorescence , quantum efficiency , benzimidazole , common emitter , photochemistry , acceptor , optoelectronics , chemistry , nanotechnology , optics , organic chemistry , physics , layer (electronics) , condensed matter physics
Abstract Although imidazole derivatives are promising as blue fluorescent emitters in organic light‐emitting devices (OLEDs), the corresponding blue thermally activated delayed fluorescence (TADF) emitter is rarely explored. In this study, a series of imidazo[1,2‐f]phenanthridine‐based TADF materials in the blue to sky‐blue region is developed. The resultant benzimidazole (BIP)‐based TADF materials, with π‐expanded acceptor and electron‐donor phenoxazine (PXZ), namely PXZ‐BIP, shows a high maximum external quantum efficiency (η ext,max ) of 21% with CIE coordinates of (0.21, 0.37). These results have clearly demonstrated that PXZ‐BIP exhibits the highest η ext,max among imidazole‐based fluorescent sky‐blue OLEDs. The corresponding imidazophenanthridine derivative, with a less π‐expanded acceptor, shows inferior OLED performances, with a η ext,max of 5.9% and CIE of (0.19, 0.30). This study provides a critical molecular design to realize high‐efficiency TADF materials based on imidazole derivatives.