Noncovalent through-space charge transfer enables efficient and stable blue electroluminescence.

Abstract

Achieving efficient and stable blue emission remains a central challenge in the development of donor-acceptor-type thermally activated delayed fluorescence (TADF) materials. Charge transfer in TADF molecules typically occurs via either noncovalent through-space interactions or covalent through-bond interactions, with control over electronic coupling key to enabling effective TADF. Through-space charge transfer (TSCT), enabled by spatially proximal, face-to-face donor-acceptor architecture, offers an appealing approach to regulating charge-transfer excited states. Here, we propose an effective strategy for blue TADF molecules that leverages a multichannel TSCT approach to enhancing reverse intersystem crossing while suppressing donor-acceptor bond cleavage. Organic light-emitting diodes (OLEDs) based on the designed molecule exhibit blue emission at 468 nanometers, a high external quantum efficiency (EQE) of 32.3% with minimal roll-off, and exceptional operational stability with a <i>T</i>₉₀ of 198.2 hours at an initial luminance of 1000 candela per square meter. Furthermore, a pure-blue TADF-sensitized fluorescent OLED using our designed molecule as a sensitizer achieves an EQE of 36.6% with narrowband emission and excellent operational stability with a <i>T</i>₉₀ exceeding 87.8 hours at an initial luminance of 1000 candela per square meter. These results establish a robust framework for designing high-performance TSCT-based blue TADF molecules.