Multiple resonance thermally activated delayed fluorescence (MR-TADF) molecules are emerging as promising candidates for high-resolution organic light-emitting diode (OLED) displays, but MR-TADF emitters always suffer from dissatisfactory rate constant of reverse intersystem crossing (kRISC) due to inherently low spin orbital coupling strength between excited singlet and triplet states. Herein, we systematically investigate the long-range charge transfer (LRCT) and heavy-atom effects on modulating the excited state natures and energy levels via integrating diversiform electron-donating units with the MR skeleton. Compared with unsubstituted analogue, newly designed MR-TADF emitters exhibit significantly boosted kRISC values and close-to-unity photoluminescence quantum yield especially for tBuBNCz-PXZ (2.5×105 s-1) and tBuBNCz-Ph-PSeZ (2.1×105 s-1). Leveraging these exceptional properties, the maximum external quantum efficiency values of tBuBNCz-PXZ and tBuBNCz-Ph-PSeZ based solution-processed OLEDs can reach 21.3% and 19.4%, which are in the first tier of reported solution-processed MR-TADF binary OLEDs without employing additional sensitizer. This study provide a framework for modulating photoelectrical properties of MR-TADF emitters through fastidiously regulating LRCT and heavy-atom effects.

This article is Open Access

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