Optimizing strategy for charge injection in the single-emitting-layer light-emitting transistor

Herein, a single-layer light-emitting transistor with a good on/off ratio of more than 10${}^6$ is presented based on the iridium complex as a light-emitter layer. Comprehensive experiments and simulations demonstrate that the thickness of the emitting layer can significantly improve the majority carrier injection in the source electrode. The electrode work function determines the minority carrier injection in the drain electrode, which is crucial for the light emission of the transistor. Furthermore, the increased source injection allows for a higher channel current, thereby increasing drain injection. Most importantly, although the above methods can improve the device channel current and light-emitting brightness, the electroluminescence efficiency cannot be optimized since the increased minority carriers are much less than the increased majority carriers, resulting in most increased majority carriers cannot be contributed to the charge recombination. To achieve a higher efficient device, the channel current is supposed to be low when a conductive channel is well formed. This goal is achieved by using an ionic liquid gate to replace SiO${}_2$ gate for fabricating the light-emitting single-layer transistor. The efficiency is improved from ≈0.1 to 1.5 cd A${}^{-1}$. This work provides a new strategy for constructing high-performance single-layer light-emitting transistors. (© 2023 Wiley‐VCH GmbH)