High-Performance Solution Processable Red TADF-OLED with External Quantum Efficiency Exceeding 28% Using a Multi-Resonance Emitter Host

초록

Achieving high-efficiency soluble red thermally activated delayed fluorescence (TADF) emitters remains a substantial challenge owing to the constraints imposed by the energy-gap law. In this study, an asymmetric pyrene-azaacene derivative, named PBCNT, is prepared and characterized, featuring a strong electron-donating tert-butyl diphenylamine moiety and an electron-withdrawing cyano group. PBCNT exhibits intense red emission with a peak wavelength of 664 nm in a toluene solution. It demonstrates an evident TADF character in the solid state, attributed to a small energy difference of 0.04 eV between its lowest singlet and triplet states. By employing a multi resonance-type TADF molecule as the host matrix, a solution-processed organic light-emitting diode (OLED) based on PBCNT achieved a record-high maximum external quantum efficiency (EQE) of 28.5%, with a red emission peak at 608 nm, facilitated by effective F & ouml;rster energy transfer, good horizontal emitting dipole orientation and managed intermolecular interactions between the host and dopant. This represents one of the highest EQE values reported among solution-processed red TADF OLEDs emitting electroluminescence at wavelengths greater than 600 nm. This paper introduces a promising pathway for developing efficient red TADF emitters that overcome the limitations of the energy-gap law.

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