Photosensitive n-Type Doping Using Perovskite CsPbX₃ Quantum Dots for Two-Dimensional MSe₂ (M = Mo and W) Field-Effect Transistors

Perovskite CsPbX₃ (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 MX₂ (M = Mo, W; X = S, Se, Te, etc.) structures have been used in flexible optoelectronic devices. In this study, perovskite green-light-emitting CsPbBr₂I₁ quantum dots (QDs) and blue-light-emitting CsPb(Cl/Br)₃-QDs are utilized to enhance the photoresponsive characteristics of 2D MSe₂ (M = Mo and W)-based field-effect transistors (FETs). From laser confocal microscopy photoluminescence (PL) experiments, PL quenching of the perovskite CsPb(Cl/Br)₃-QDs and CsPbBr₂I₁-QDs is observed after hybridization with MoSe₂ and WSe₂ layers, respectively, which reflects the charge-transfer effect. According to the characteristics of the FETs based on the WSe₂, MoSe₂, WSe₂/CsPbBr₂I₁-QDs hybrid, and MoSe₂/CsPb(Cl/Br)₃-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 MoSe₂ and WSe₂ nanosystems originates from the photogating effect by the trap states after the hybridization with various perovskite CsPbX₃-QDs.