Managing Charge Transport and Exciton Generation for Highly Efficient, Bright, and Stable Near-Infrared Organic Radical

Near-infrared (NIR) organic light-emitting diodes based on open-shell radical emitters offer a spin-allowed pathway to high-brightness emission. However, their practical implementation has been hindered by efficiency roll-off at high current densities. Here, we demonstrate that simultaneously achieving balanced charge transport and high emission efficiency is key to overcoming this limitation in radical-based electroluminescence. By contrasting conventional exciplex-based reference systems with a thermally activated delayed fluorescence (TADF)-based architecture, we identify a trade-off between charge balance and photoluminescence efficiency arising from exciplex-mediated excitation pathways in radical electroluminescence. Leveraging efficient energy transfer from the TADF material while maintaining charge balance, we achieve a high external quantum efficiency of 8.1% at 804 nm, with over 5% EQE at a high current density of 100 mA cm⁻². Coupled Poisson and drift–diffusion modeling of device operation matches experimental observations and indicates that roll-off at high current densities is due primarily to quenching of doublet excitons by holes. This work establishes a TADF-assisted exciton management strategy for NIR radical electroluminescence and highlights its potential for next-generation NIR optoelectronic technologies.