TY - JOUR
T1 - Highly Efficient Deep-Blue Organic Light-Emitting Diodes Based on Rational Molecular Design and Device Engineering
AU - Mamada, Masashi
AU - Katagiri, Hiroshi
AU - Chan, Chin Yiu
AU - Lee, Yi Ting
AU - Goushi, Kenichi
AU - Nakanotani, Hajime
AU - Hatakeyama, Takuji
AU - Adachi, Chihaya
N1 - Funding Information:
The authors thank Ms. K. Kusuhara and Ms. N. Nakamura for the characterization of materials. The authors acknowledge support from JSPS Core‐to‐Core Program (JPJSCCA20180005). M.M. acknowledged financial support from JSPS KAKENHI Grant Number 19H02790, 20K21227, and 21H05401.
Publisher Copyright:
© 2022 Wiley-VCH GmbH.
PY - 2022/8/8
Y1 - 2022/8/8
N2 - There is increasing interest in thermally activated delayed fluorescence (TADF) in materials, and to understand its mechanism in the excited state dynamics. Recent challenges include color purity, efficient deep-blue emission, fast exciton decay lifetimes, high reverse intersystem crossing rates (kRISC), low-efficiency roll-off in organic light-emitting diodes (OLEDs), and long device lifetimes. Here, a series of compounds having benzonitrile and carbazole rings are examined, that provide a detailed understanding of the excited states, and a guideline for high-performance TADF. A dense alignment of the excited states with several different characters within a small energy range results in high kRISC of >2 × 106 s−1, while maintaining radiative rate constants (kr) >107 s−1. OLEDs based on the optimum compound exhibit a low-efficiency roll-off and a CIEy (y color coordinate of Commission Internationale de l'Éclairage) <0.4. TADF-assisted fluorescence (TAF) OLED exhibits a maximum external quantum efficiency of 22.4% with CIE coordinates (0.13,0.15). This work also provides insights for device engineering and molecular designs.
AB - There is increasing interest in thermally activated delayed fluorescence (TADF) in materials, and to understand its mechanism in the excited state dynamics. Recent challenges include color purity, efficient deep-blue emission, fast exciton decay lifetimes, high reverse intersystem crossing rates (kRISC), low-efficiency roll-off in organic light-emitting diodes (OLEDs), and long device lifetimes. Here, a series of compounds having benzonitrile and carbazole rings are examined, that provide a detailed understanding of the excited states, and a guideline for high-performance TADF. A dense alignment of the excited states with several different characters within a small energy range results in high kRISC of >2 × 106 s−1, while maintaining radiative rate constants (kr) >107 s−1. OLEDs based on the optimum compound exhibit a low-efficiency roll-off and a CIEy (y color coordinate of Commission Internationale de l'Éclairage) <0.4. TADF-assisted fluorescence (TAF) OLED exhibits a maximum external quantum efficiency of 22.4% with CIE coordinates (0.13,0.15). This work also provides insights for device engineering and molecular designs.
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U2 - 10.1002/adfm.202204352
DO - 10.1002/adfm.202204352
M3 - Article
AN - SCOPUS:85130254804
SN - 1616-301X
VL - 32
JO - Advanced Functional Materials
JF - Advanced Functional Materials
IS - 32
M1 - 2204352
ER -