Enhanced ambipolar charge transport for efficient organic single crystal light-emitting transistors with narrowed ambipolar regime

Organic light-emitting transistors (OLETs) are attractive advanced devices but their use is currently limited by multiple challenges, including the absence of ambipolar emissive organic semiconductors and difficulty in achieving balanced ambipolar transport toward high efficiency. Here, we show that efficient ambipolar OLETs can be obtained using a high hole mobility organic semiconductor, 2,6-diphenylanthracene (DPA) via energy-level engineering. Both electron and hole charge injection barriers, Vth,h and Vth,e were significantly reduced leading to a narrower ambipolar regime and high and balanced ambipolar transport. The OLETs exhibited efficient and stable light emission in their conducting channel not in the vicinity of electrodes. Moreover, the excellent consistency of the maximum electroluminescence intensity and minimum source–drain current of the OLETs resulted in high external quantum efficiency at low voltage, providing solid evidence for the efficient charge recombination in these devices under ambipolar conditions. This result suggests the importance of achieving ambipolar charge transport with a narrowed ambipolar regime for high-efficiency OLETs and their related integrated optoelectronic devices/circuits.