Design of Efficient Benzosilole Derivatives for Tuning High-Performance HLCT OLEDs.

Properties of hybridized local and charge-transfer (HLCT) materials can be tuned by adjusting locally excited (LE) and charge-transfer (CT) components, resulting in either quasi-equivalent hybridization or non-equivalent hybridization. These HLCT materials are easily designed on the molecular level to be applied in organic light-emitting diodes (OLEDs), which have advantages in the aspects of external quantum efficiency (EQE), efficiency roll-off, and color purity. In previous work, an HLCT silole derivative with an electron donor (D) - acceptor (A) structure modified at 1-position achieved a breakthrough in the external quantum efficiency (EQE) of 9.1%. Whereas such molecular design generally leads to low PLQYs, limiting the further improvement of EQE. Thinking a more rigid structure design strategy, in this work, silole is replaced with a more rigid benzosilole structure that is selectively modified by a carbazole (Cz) or 9,9-dimethyl-9,10-dihydroacridine (Ac) unit as donor and triazine (TRZ) unit as the acceptor, leading to higher PLQYs of the CT-like HLCT molecule DCz-BS-TRZ, and quasi-equivalent HLCT molecule DAc-BS-TRZ. Among these two molecules, the DCz-BS-TRZ-based OLED device has shown a remarkable 13% EQE, which is the highest EQE for silole-based OLEDs.