Open AccessHighly Efficient and Stable Blue Organic Light‐Emitting Diodes based on Thermally Activated Delayed Fluorophor with Donor‐Void‐Acceptor Motif
Author(s) -
Zhang Dongdong,
Wada Yoshimasa,
Wang Qi,
Dai Hengyi,
Fan Tianjiao,
Meng Guoyun,
Wei Jinbei,
Zhang Yuewei,
Suzuki Katsuaki,
Li Guomeng,
Duan Lian,
Kaji Hironori
Publication year - 2022
Publication title -
advanced science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.388
H-Index - 100
ISSN - 2198-3844
DOI - 10.1002/advs.202106018
Subject(s) - delocalized electron , acceptor , fluorophore , oled , materials science , photochemistry , carbazole , quantum efficiency , fluorescence , optoelectronics , chemistry , nanotechnology , optics , physics , organic chemistry , layer (electronics) , condensed matter physics
Thermally activated delayed fluorophores (TADF) with donor–acceptor (D‐A) structures always face strong conjugation between donor and acceptor segments, rendering delocalized new molecular orbitals that go against blue emission. Developing TADF emitters with blue colors, high efficiencies, and long lifetimes simultaneously is therefore challenging. Here, a D‐void‐A structure with D and A moieties connected at the void‐position where the frontier orbital from donor and acceptor cannot be distributed, resulting in nonoverlap of the orbitals is proposed. A proof‐of‐the‐concept TADF emitter with 3,6‐diphenyl‐9 H ‐carbazole (D) connected at the 3’3‐positions of 9 H ‐xanthen‐9‐one (A), the void carbon‐atom with no distribution of the highest occupied molecular orbital (HOMO) of A‐segment, realizes more efficient and blue‐shifted emission compared with the contrast D‐A isomers. The deeper HOMO‐2 of A is found to participate into conjugation rather than HOMO, providing a wider‐energy‐gap. The corresponding blue device exhibits a y color coordinate (CIE y ) of 0.252 and a maximum external quantum efficiency of 27.5%. The stability of this compound is further evaluated as a sensitizer for a multiple resonance fluorophore, realizing a long lifetime of ≈650 h at an initial luminance of 100 cd m −2 with a CIE y of 0.195 and a narrowband emission with a full‐width‐at‐half‐maxima of 21 nm.