Engineering an Injecting Layer for Light-Emitting Field Effect Transistors

Light-emitting field effect transistors (LEFETs) integrate transistor logic with the light emission of an organic light-emitting diode (OLED). Their dual functionality has the potential to simplify circuitry in several high-end applications, such as next generation displays. LEFETs incorporate a wide range of materials as the charge transporting and light-emitting layers within its complex device architecture. These include small molecules, polymers, single crystals, oxides and perovskites. However, LEFETs reported to-date suffer from poor external quantum efficiencies (EQEs), as balanced charge transport and injection into the light-emitting layer are difficult to realise.<br/><br/>Herein, we report an effective method for improving charge injection into hybrid LEFETs, comprising a n-type metal oxide layer for electron transport and a conjugated polymer for light emission. LEFETs exhibit charge carrier mobilities in the range of 10 cm²V^-1s^-1, on/off ratios above 10⁵ and low threshold voltages. Furthermore, a maximum EQE of 2 % was achieved at a brightness of 2500 cdm^-2. These devices show a significant improvement in key performance parameters and are a significant step towards the development of highly efficient LEFET technology.