Journal
ADVANCED FUNCTIONAL MATERIALS
Volume 32, Issue 32, Pages -Publisher
WILEY-V C H VERLAG GMBH
DOI: 10.1002/adfm.202204352
Keywords
DABNA; hyperfluorescence; organic light-emitting diodes; reverse intersystem crossing; TADF
Categories
Funding
- JSPS Core-to-Core Program [JPJSCCA20180005]
- JSPS KAKENHI [19H02790, 20K21227, 21H05401]
- Grants-in-Aid for Scientific Research [19H02790, 21H05401, 20K21227] Funding Source: KAKEN
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There is a growing interest in thermally activated delayed fluorescence (TADF) in materials, and this study provides insights into the properties of compounds and guidelines for high-performance TADF. It also offers implications for device engineering and molecular designs.
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 (k(RISC)), 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 k(RISC) of >2 x 10(6) s(-1), while maintaining radiative rate constants (k(r)) >10(7) 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'eclairage) <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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