Managing Charge Transport and Exciton Generation for Highly Efficient, Bright, and Stable Near‐Infrared Organic Radical Light‐Emitting Diodes

ABSTRACT 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. Leveraging efficient energy transfer from the TADF material while maintaining charge balance, we achieve a high external quantum efficiency (EQE) 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.