Two‐in‐One Molecule as a Single‐Molecule Exciplex Host for Enhancing Solution‐Processed TADF‐OLED Performance

Abstract Exciplexes that exhibit efficient reverse intersystem crossing have attracted considerable attention as host materials for high‐performance organic light‐emitting diodes (OLEDs). However, conventional binary exciplexes, composed of p‐ and n‐type hosts and typically designed for vacuum deposition, are not suitable for solution‐processed OLEDs owing to their low solubilities, poor film‐forming properties, and phase‐separation tendencies. In this study, the development of a novel “two‐in‐one” (TIO) is reported molecule that functions as a single‐molecule exciplex host and is synthesized by covalently linking p‐ and n‐type moieties via a non‐conjugated spacer. First, this molecular design preserves the intrinsic electronic and photophysical properties of both the p‐ and n‐type units while enabling efficient exciplex formation in thin films. Second, the TIO exciplex host exhibits excellent solubility, thermal stability, and film‐forming properties, making it highly suitable for solution‐processed OLEDs. Finally, a TIO exciplex host‐based device with a green emitter delivers a higher external quantum efficiency (31.06%) than that of a binary exciplex host‐based device. This improved device performance is attributable to the high photoluminescence quantum yield (87%) of the emitting layer and its excellent charge balance. This study demonstrates the potential of a single‐molecule exciplex host for enhancing OLED efficiency while providing a simplified fabrication process.