Tetracyano-substituted spiro[fluorene-9,9′-xanthene] as electron acceptor for exciplex thermally activated delayed fluorescence

Herein, a tetracyano-substituted spiro[fluorene-9,9′-xanthene] (SFX) derivative, 2,3′,6′,7-tetracarbonitrile-SFX (TCNSFX) was conveniently synthesized as electron acceptor for combining with tris(4-carbazoyl-9-ylphenyl)amine (TCTA) as electron donor to form exciplex emitter. Subsequently, exciplex-TADF was successfully realized with photoluminescence quantum yield of 29% and electroluminescence efficiency of 6.0 cd A⁻¹ in TCTA:TCNSFX. The exciplex-TADF performance of TCTA:TCNSFX is related to the stronger electron-accepting ability through tetracyano-substitution and large driving force in the exciplex emission. Although the emission efficiencies are slightly low, this work enriches the design system of electron acceptors for exciplex-TADF, simultaneously offering an efficient and convenient approach to developing low-cost materials and devices for TADF.