This project recently develops a highly efficient and cost-effective multiple resonance thermally activated delayed fluorescence (MR-TADF) material, TAzBN,^[1] which offers high resource availability and improved environmental sustainability. TAzBN utilizes ambient thermal energy to facilitate singlet-triplet transitions, enhancing emission efficiency without relying on expensive and scarce heavy metals such as iridium and platinum for efficient photoluminescence.^[2-3]

The rigid backbone of TAzBN effectively suppresses non-radiative decay, achieving a remarkable photoluminescence quantum yield of 94%. Its embedded azepine unit enhances intramolecular charge transfer and spin-orbit coupling,^[4] resulting in a reverse intersystem crossing (RISC) rate of 8.50 × 10⁵ s⁻¹. Additionally, the chiral isomers of TAzBN exhibit circularly polarized luminescence (CPL) in thin films, with a dissymmetry factor of 1.07 × 10⁻³. This property originates from its unique curved seven-membered ring structure, which not only suppresses aggregation-induced quenching but also enhances chiroptical properties. Compared to conventional materials, CPL-TADF can improve light utilization efficiency without additional optical filters,^[5] reducing energy consumption and promoting more sustainable optoelectronic technologies.

Organic light emitting diodes (OLEDs) based on TAzBN achieve a maximum external quantum efficiency (EQE) of 27.3%, approaching the theoretical limit of TADF-based devices. Even at a high brightness of 500 cd/m², the EQE remains at 21.4%, demonstrating exceptional efficiency stability. This highly efficient and stable emission performance reduces energy consumption in displays and lighting, lowers carbon emissions, and minimizes electronic waste, aligning with green energy initiatives.