P‐Type SnO Thin Film Phototransistor with Perovskite‐Mediated Photogating

A p‐type phototransistor based on tin monoxide (SnO) thin film and a perovskite‐mediated photogating effect to enhance the device performance are reported. Without the perovskite layer, the SnO thin film phototransistor exhibits a good figure of merit including on/off ratio ( I on / I off ) over 10 3 , hole mobility of 3.55 cm 2 V −1 s −1 , photoresponsivity of 1.83 × 10 3 A W −1 , and detectivity of 2.11 × 10 13 Jones at 655 nm; these values are among the highest reported for oxide‐based devices. Furthermore, it is shown that when a hybrid perovskite MAPbI 3 overlayer is deposited on the p‐type SnO channel, the phototransistor behavior is significantly modified. Specifically, the field‐effect mobility increases to 5.53 cm 2 V −1 s −1 and the on/off ratio increases to 2.7 × 10 3 compared with an on/off ratio of 519 under dark. These effects can be ascribed to a perovskite‐mediated photogating effect with favorable band alignment and interfacial charge transfer. This work not only introduces SnO as a new p‐type phototransistor material but also presents a general approach to enhance the channel transport via coating a photoactive perovskite overlayer.