Highly Efficient and Bright Blue OLEDs via TSCT‐TADF Molecule Regulated by Indolo[3,2,1‐jk]Carbazole

Abstract Thermally activated delayed fluorescence (TADF) materials with the through‐space charge transfer (TSCT) effects can provide a useful approach to efficiently utilize dark state triplet excitons through an efficient reverse intersystem crossing process. TSCT‐TADF emitters PCzoTrz‐ICz with small ∆E_ST values and high photoluminescence quantum yield is designed and synthesized using common acceptor triazine, donor 3,6‐diphenylcarbazole and Indolo[3,2,1‐jk]carbazole which is a rigid π‐conjugated group with high triplet state and high thermal stability. The doped‐organic light‐emitting diodes using PCzoTrz‐ICz as emitters exhibit high tolerance to host with different polarity and charge transport properties, and PCzoTrz‐ICz doped devices in 2,8‐bis(diphenylphosphoryl)dibenzofuran even realizes a maximum external quantum efficiency (EQE_max) of 32.5% and maximum current efficiency (CE_max) of 74.1 cd A⁻¹, which is higher than EQE_max of 28.1% and CE_max of 64.8 cd A⁻¹ of PCzoTrz. Moreover, PCzoTrz‐ICz can be used as highly efficient sensitizers for narrow band blue emitter of v‐DABNA, and achieves more than EQE_max of 33.3%, maximum luminance of 26,291 cd m⁻², CE_max of 42.7 cd A⁻¹ and blue index of 237 cd A⁻¹ CIE_y⁻¹.