Versatile benzthienocarbazole isomer derivatives as efficient TADF emitters and hosts for blue multi-resonance TADF emitters

• All emitters with both TSCT and TBCT characteristics. • The balanced TSCT and TBCT ratios resulting in high of above 95%. • High EQE of 24.1% was achieved for the device using 32cBTC-TRZ as emitter. • The device using 32cBTC-TRZ as host exhibited high efficiency of 37.5%. Organic light-emitting diodes garnered significant attention due to their commercial application in flat panel displays. Herein, versatile benzthienocarbazole isomer derivatives are reported as highly efficient emitters and host materials for blue multi-resonance thermally activated delayed fluorescence emitters. It is observed that the ortho -connected benzthienocarbazole donor and triazine acceptor units impart the emitters with both through-bond charge transfer (TBCT) and through-space charge transfer (TSCT), allowing for modulation of photophysical and electronic properties by varying the benzthienocarbazole isomer donors. The emitters 23bBTC-TRZ and 32cBTC-TRZ featuring 7H-benzo[4,5]thieno[2,3-b]carbazole and 5H-benzo[4,5]thieno[3,2-c]carbazole donor units, respectively, exhibit balanced TSCT/TBCT ratios, thereby imparting a high photoluminescence quantum yield exceeding 95 %. Consequently, a maximum external quantum efficiency of 24.1 % is achieved for the device based on 32cBTC-TRZ as emitter. Furthermore, when utilizing 32cBTC-TRZ as the host and v-DABNA as the terminal emitter, a remarkable efficiency of 37.5 % is attained, characterized by a narrowband emission with a full width at half maximum (FWHM) of 24 nm.