Enhanced amplified spontaneous emission and electroluminescence from C545T emissive layers via exciplex sensitization

Organic semiconductor lasers (OSLs) have attracted considerable attention due to promising applications in optoelectronics. A critical challenge for realizing electrically pumped OSLs is the synergistic enhancement of optical amplification capability and electroluminescence (EL) efficiency in organic gain media. In this study, a TCTA: TPBi exciplex is employed as a sensitizer to construct an efficient gain medium based on C545T. Compared with the unsensitized reference blend film, the incorporation of the TCTA: TPBi exciplex reduces the amplified spontaneous emission (ASE) threshold by 50% and enhances the optical gain by twofold. When applied to organic light-emitting diodes (OLEDs), the exciplex sensitized emissive layer (EML) achieves a maximum luminance of 8989 cd/m² at the optimal doping ratio, representing an improvement of more than two times relative to the reference device. The enhanced ASE performance and improved optoelectronic characteristics of OLEDs originate from efficient Förster resonance energy transfer (FRET) between exciplex and C545T molecules, optimized molecular orientation, and an improved balance of charge carrier injection and transport. This work demonstrates that the exciplex sensitization strategy can simultaneously enhance both optical amplification and EL performance in organic emissive systems, offering a viable approach toward high-performance electrically pumped OSLs.