Bulky neutral group incorporation in Through-Space charge transfer delayed fluorescence emitters for efficient Non-Doped organic Light-Emitting diodes

The development of non-doped through-space charge transfer thermally activated delayed fluorescent (TSCT-TADF) materials remains a significant challenge, with only limited examples reported to date. Herein, we present an innovative approach to enhance the efficiency of non-doped organic light-emitting diodes (OLEDs) by integrating a bulky neutral m-terphenyl or tetraphenylsilicon unit into the TSCT-TADF core. The installation of a rigid bulky group not only disturbs the intermolecular π-π stacking but also alleviates exciton quenching in the aggregate state. These materials show distinct aggregation-induced emission characteristics and achieve a high photoluminescence quantum yield in neat films. These properties enable the realization of highly efficient doped OLEDs with an external quantum efficiency (EQE) exceeding 30%. Importantly, non-doped devices achieve a record-high EQE of 21.4% with minimal efficiency roll-off. The design strategy employing rigid bulky shielding demonstrated in this study proves to be a promising approach for the development of efficient non-doped TSCT-TADF emitters.