Excited-State Engineering of Chalcogen-Bridged Chiral Molecules for Efficient OLEDs with Diverse Luminescence Mechanisms.

The exploration of circularly polarized luminescence is important for advancing display and lighting technologies. Herein, by utilizing isomeric molecular engineering, a novel series of chiral molecules are designed to exploit both thermally activated delayed fluorescence (TADF) and room-temperature phosphorescence (RTP) mechanisms for efficient luminescence. The cooperation of a small singlet-triplet energy gap, moderate spin-orbital coupling (SOC), and large oscillator strength enables efficient TADF emission, with photoluminescence quantum yields exceeding 90 %. By altering the symmetry of molecular structures, it is demonstrated that the intrinsic electronic SOC and vibrational SOC effects can be greatly enhanced to facilitate RTP emission. Notably, through modulating simultaneous TADF and RTP emissions, single-molecule white emission is successfully achieved. Accordingly, the TADF-based organic light-emitting diode (OLED) achieves a maximum external quantum efficiency up to 30 %, representing exceptional performance of non-aromatic amine-based emitters. Furthermore, the first single-molecule white OLED based on TADF and RTP dual-emissive chiral material is developed, establishing a benchmark for the development of advanced display and lighting technologies.