Twisted Structure and Multiple Charge-Transfer Channels Endow Thermally Activated Delayed Fluorescence Devices with Small Efficiency Roll-Off and Low Concentration Dependence.

Chem Asian J

Jiangsu Key Laboratory for Carbon-Based Functional Materials & Devices, Institute of Functional Nano & Soft Materials (FUNSOM), Soochow University, Suzhou, Jiangsu, 215123, P. R. China.

Published: November 2024

Despite the rapid development of thermally activated delayed fluorescent (TADF) materials, developing organic light-emitting diodes (OLEDs) with small efficiency roll-off remains a formidable challenge. Herein, we have designed a TADF molecule (mClSFO) based on the spiro fluorene skeleton. The highly twisted structure and multiple charge-transfer channels effectively suppress aggregation-caused quenching (ACQ) and endow mClSFO with excellent exciton dynamic properties to reduce efficiency roll-off. Fast radiative rate (k) and rapid reverse intersystem crossing (RISC) rate (k) of 1.6×10 s and 1.07×10 s, respectively, are obtained in mClSFO. As a result, OLEDs based on mClSFO obtain impressive maximum external quantum efficiency (EQE) exceeding 20 % across a wide doping concentration range of 10-60 wt %. 30 wt % doped OLED exhibits an EQE of 23.1 % with a small efficiency roll-off, maintaining an EQE of 18.6 % at 1000 cd m. The small efficiency roll-off and low concentration dependence observed in the TADF emitter underscore its significant potential.

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Source
http://dx.doi.org/10.1002/asia.202400679DOI Listing

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