Photosensitive n-Type Doping Using Perovskite CsPbX Quantum Dots for Two-Dimensional MSe (M = Mo and W) Field-Effect Transistors.

Perovskite CsPbX (X = Br, Cl, and I) nanostructures have been intensively studied as they are luminescent, photovoltaic, and photosensitizing active materials. Two-dimensional (2D) transition-metal dichalcogenides (TMDCs) with MX (M = Mo, W; X = S, Se, Te, etc.) structures have been used in flexible optoelectronic devices. In this study, perovskite green-light-emitting CsPbBrI quantum dots (QDs) and blue-light-emitting CsPb(Cl/Br)-QDs are utilized to enhance the photoresponsive characteristics of 2D MSe (M = Mo and W)-based field-effect transistors (FETs). From laser confocal microscopy photoluminescence (PL) experiments, PL quenching of the perovskite CsPb(Cl/Br)-QDs and CsPbBrI-QDs is observed after hybridization with MoSe and WSe layers, respectively, which reflects the charge-transfer effect. According to the characteristics of the FETs based on the WSe, MoSe, WSe/CsPbBrI-QDs hybrid, and MoSe/CsPb(Cl/Br)-QDs hybrid, the p-channel current (with hole mobility) is considerably decreased after the hybridization with the QDs. Notably, under incident light, the n-channel photocurrent and photoresponsivity of the FET are substantially increased, and the threshold voltage is negatively shifted owing to the hybridization with the perovskite QDs. The results show that the photosensitive n-type doping effect on the 2D MoSe and WSe nanosystems originates from the photogating effect by the trap states after the hybridization with various perovskite CsPbX-QDs.