Electroplex Emission in TADF-Based Organic Light-Emitting Transistors

Thermally activated delayed fluorescence (TADF) offers promising routes to enhance the efficiency of organic light-emitting devices by enabling utilization of both triplet and singlet excitons. In this study, we investigate the performance of multilayer organic heterostructures incorporating the TADF emitter DMAC-DPS blended with CBP, under field-effect charge transport conditions in transistor-based devices. We systematically studied the optical and electronic properties of emissive blends within the device architecture. Two key findings emerge from this study: (a) a DMAC-DPS concentration of 15% yields the highest electroluminescence efficiency, which we attribute to balanced charge transport within the emissive layer, and (b) electrical excitation induces a pronounced red shift in the emission spectrum, suggesting electroplex formation at the interface between the emissive blend and the n-type semiconductor. These results highlight the critical role of balanced charge transport and interfacial interactions for the understanding of light generation mechanisms and overall improvement of the device performances while offering new insights into the design of TADF-based light-emitting transistors.