TY - JOUR
T1 - Modulation of OLED efficiency
T2 - Via a combination of aromatic electrophilic directing and intramolecular charge transfer
AU - Nie, Xiancheng
AU - Wang, Tao
AU - Huang, Wenhuan
AU - Su, Hao
AU - Chen, Biao
AU - Zhang, Xuepeng
AU - Zhang, Guoqing
N1 - Publisher Copyright:
© The Royal Society of Chemistry.
PY - 2021/11/21
Y1 - 2021/11/21
N2 - Thermally activated delayed fluorescence (TADF) materials utilizing purely organic compounds have become a promising and more eco-friendly alternative to phosphorescent organometallic emitters in organic light-emitting diode (OLED) devices. However, the modulation of luminescence properties for molecules with a high degree of structural complexity remains challenging. Herein, by combining the aromatic electrophilic directing (AED) and intramolecular charge transfer (ICT) effects, two OLED emitters containing an electron donor (triphenylamine, TPA) and acceptor (benzophenone) covalently linked via a carbazole ring were synthesized and compared. The design concomitantly allows for spatial separation of origin/destination orbitals involved in the lowest singlet excited state and increased density of charge carriers in contrast to a non-conjugated linker. More conveniently, we demonstrate that increased acceptor strength by cyano-substitution results in a significant decrease of the singlet-triplet energy gap from 0.23 to 0.09 eV. The latter exhibits a TADF photoluminescence quantum yield of up to 63% with a lifetime of 7.67 μs in the OLED matrix. Notably, the OLED device using the cyano-TADF molecules as the emitting layer possesses an enhanced external quantum efficiency of 15.6%, compared to 10.3% efficiency obtained from the non-substituted version, and small efficiency roll-off, demonstrating the modulation versatility of purely organic molecule-based OLED devices.
AB - Thermally activated delayed fluorescence (TADF) materials utilizing purely organic compounds have become a promising and more eco-friendly alternative to phosphorescent organometallic emitters in organic light-emitting diode (OLED) devices. However, the modulation of luminescence properties for molecules with a high degree of structural complexity remains challenging. Herein, by combining the aromatic electrophilic directing (AED) and intramolecular charge transfer (ICT) effects, two OLED emitters containing an electron donor (triphenylamine, TPA) and acceptor (benzophenone) covalently linked via a carbazole ring were synthesized and compared. The design concomitantly allows for spatial separation of origin/destination orbitals involved in the lowest singlet excited state and increased density of charge carriers in contrast to a non-conjugated linker. More conveniently, we demonstrate that increased acceptor strength by cyano-substitution results in a significant decrease of the singlet-triplet energy gap from 0.23 to 0.09 eV. The latter exhibits a TADF photoluminescence quantum yield of up to 63% with a lifetime of 7.67 μs in the OLED matrix. Notably, the OLED device using the cyano-TADF molecules as the emitting layer possesses an enhanced external quantum efficiency of 15.6%, compared to 10.3% efficiency obtained from the non-substituted version, and small efficiency roll-off, demonstrating the modulation versatility of purely organic molecule-based OLED devices.
UR - https://www.scopus.com/pages/publications/85118646294
U2 - 10.1039/d1tc04156h
DO - 10.1039/d1tc04156h
M3 - Article
AN - SCOPUS:85118646294
SN - 2050-7526
VL - 9
SP - 15698
EP - 15706
JO - Journal of Materials Chemistry C
JF - Journal of Materials Chemistry C
IS - 43
ER -