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

초록

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.

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