Highly efficient exciplex-emission from spiro[fluorene-9,9′-xanthene] derivatives

Exciplex-thermally activated delayed fluorescence (TADF) is significant due to its potential in energy-saving and flexible techniques, but still suffers from complicated-synthesis materials and low-efficiency devices. Herein, we synthesize two new spiro[fluorene-9,9′-xanthene] (SFX)-based acceptors, 2-(4,6-diphenyl-1,3,5-triazin-2-yl)-SFX (TRZSFX) and 2,7-bis(4,6-diphenyl-1,3,5-triazin-2-yl)-SFX (DTRZSFX) via convenient method, and obtain exciplex-emitters using the tris(4-carbazoyl-9-ylphenyl)amine (TCTA) as a donor. The results suggest that two devices based on TCTA:TRZSFX and TCTA:DTRZSFX display excellent exciplex-TADF accompanied by appealing efficiencies of 79.6 cd A⁻¹ and 78.1 lm W⁻¹. Encouragingly, a maximum value of 22.5% in external quantum efficiency (EQE) is realized for TCTA:TRZSFX-based device, which is higher than those of most reported exciplex OLEDs as far as we know. Our work offers a promising avenue for developing high-efficiency exciplex-emissions.