Synthesis and properties of binaphthyl chiral thermally activated delayed fluorescence molecules using thioxanthone as acceptor

摘要

The currently reported axial chiral molecules based on the 3,3 ' -substitution of the binaphthyl skeleton are limited by intrinsic fluorescence properties, resulting in generally low device efficiencies (EQE < 5%) of related organic light emitting diodes (OLEDs). Herein, we designed and synthesized four pair of chiral binaphthyl enantiomers ( R/S - 1 - R/S - 4 ) adopting acceptor-donor-donor-acceptor (ADDA) structure by introducing different thioxanthone modification groups on the 3,3 ' -position of 2,2 ' -dimethoxy1,1 ' -binaphthalene. Among them, emitter R/S - 2 and R/S - 4 obtained by enhancing intramolecular charge transfer exhibited TADF characteristics due to relatively small AE ST of 0.12 eV and 0.17 eV, and relatively moderate SOC matrix elements of 0.28 cm(-1) and 0.10 cm(-1) between the (CT)-C-1 and (LE)-L-3 states. The CD spectra of these enantiomers in diluted solutions showed perfect mirror images and reasonable g abs for small organic molecules (10 -4 -10 -3 ). And the external quantum efficiencies (EQE) of 10.9% and 8.32% for device A and B based on emitter S - 2 and S - 4 were highest compared with currently reported axial chiral molecules based on the 3,3 ' -position substitution of binaphthyl skeleton, providing simple molecular design strategies to construct efficient CP-OLED device.

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