Room‐Temperature Halide Perovskite Field‐Effect Transistors by Ion Transport Mitigation

Abstract Solution‐processed halide perovskites have emerged as excellent optoelectronic materials for applications in photovoltaic solar cells and light‐emitting diodes. However, the presence of mobile ions in the material hinders the development of perovskite field‐effect transistors (FETs) due to screening of the gate potential in the nearby perovskite channel, and the resulting impediment to achieving gate modulation of an electronic current at room temperature. Here, room‐temperature operation is demonstrated in cesium lead tribromide (CsPbBr₃) perovskite‐based FETs using an auxiliary ferroelectric gate of poly(vinylidenefluoride‐co‐trifluoroethylene) [P(VDF‐TrFE)], to electrostatically fixate the mobile ions. The large interfacial polarization of the ferroelectric gate attracts the mobile ions away from the main nonferroelectric gate interface, thereby enabling modulation of the electronic current through the channel by the main gate. This strategy allows for realization of the p‐type CsPbBr₃ channel and revealing the thermally activated nature of the hole charge transport. The proposed strategy is generic and can be applied for regulating ions in a variety of ionic–electronic mixed semiconductors.