Understanding Charge Transport in All-Inorganic Halide Perovskite Nanocrystal Thin-Film Field Effect Transistors

Improving devices based on solution-processed halide perovskite nanocrystals (NCs) demands a deeper understanding of charge transport in this emerging new class of ionic semiconductor nanomaterials. In this work, we fabricate all-inorganic CsPbBr3 NCs terminated with short ligands into field effect transistors, providing a facile platform to study the electronic-ionic transport systematically. By combining with transient response characterization, we demonstrate that electronic current is the dominant current passing through perovskite-NC films under dark conditions, while mobile ions induce intrinsic doping to perovskite NCs, which gradually changes the film conductivity and thereby the magnitude of the electronic current. The ion-induced doping prevails over the gating effect at room temperature, resulting in no gate modulation of the channel current in the transistor measurements. At T < 240 K, however, when ionic transport is suppressed, CsPbBr,-NC transistors exhibit a clean unipolar transport characteristic in a p-type mode featuring well-defined linear and saturation regimes. Extrinsically Bi3+ and Ag+-doped CsPbBr3-NC films further confirm the p-type transport property and dominant electrical gating effect at low temperature, which enables switching the device from normally off (p-type enhancement) to normally on (p-type depletion).