Photosensitive Field-Effect Transistor with Enhanced PhotoamplificationMediated by Charge Transfer in a Heterostructure of?-CsPbI3Nanocrystals andTwo-Dimensional WS2 br

Hybrid heterostructure-based phototransistors are attractive owing to their high gain induced by thephotogating effect. However, the absence of an in-plane built-in electric field in the single-channel-layer transistor results in a relatively higher dark current and requires a large operating gate voltageof the device. Here, we report air-stable cesium lead iodide/tungsten di-sulfide (CsPbI3/WS2)mixed-dimensional heterostructure-based photo-field-effect-transistors (photo-FETs) with asymmetric metalelectrodes (Cr/WS2/Au), exhibiting extremely low dark current (approximately 10-12A) with a respon-sivity of approximately 102A/W at zero gate bias. The Schottky-barrier- (WS2/Au interface) inducedrectification characteristics in the channel accompanied by the excellent photogating effect from solution-processed alpha-phase CsPbI3nanocrystal sensitizers, resulting in gate-tunable broadband photodetection witha very high responsivity (approximately 104A/W) and excellent sensitivity (approximately 106). Mostinterestingly, the device shows superior performance even under high-humidity (50-65%) conditionsowing to the formation of cubic alpha-phase CsPbI3nanocrystals with a relatively smaller lattice constant(a=6.2315 angstrom) and filling of surface vacancies (Pb2+centers) with the sulphur atoms from the WS2layer, thus protecting it from environmental degradation. These results emphasize an exciting strategyfor developing mixed-dimensional hybrid heterostructure-based phototransistors for futuristic integratednano-optoelectronic systems.