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.