Theoretical Studies of Electronic and Optical Behaviors of All-Inorganic CsPbI3 and Two-Dimensional MS2 (M = Mo, W) Heterostructures

Two-dimensional transition-metal dichalcogenides are not only promising optoelectronic materials but also can improve the optoelectronic performances of perovskites by forming heterostructures. Here, the structural, electronic, and optical properties of four kinds of CsPbI 3 /MS 2 (M = Mo, W) heterostructures have been comprehensively investigated by density functional theory. No matter what the heterostructure structures, the electronic structure and excellent transport properties of both CsPbI 3 surface and monolayer MS 2 can be preserved in the CsPbI 3 /MS 2 heterostructures. Moreover, CsPbI 3 /MS 2 heterostructures show type-II band alignment with indirect band gaps and charge transfers, which separate electrons and holes spontaneously. The light absorptions of CsPbI 3 surfaces in the infrared, visible, and ultraviolet regions are enhanced upon forming heterostructures. Note that the performances of heterostructures are strongly dependent on the heterostructure structure. Pb–I-terminated CsPbI 3 /MS 2 heterostructures exhibit lower tunneling barriers and larger band offsets, which may lead to higher circuit voltages and lower dark currents, but they show lower stabilities compared with Cs–I-terminated CsPbI 3 /MS 2 heterostructures. Moreover, CsPbI 3 /MoS 2 heterostructures demonstrate higher electric and optical performances than those of CsPbI 3 /WS 2 heterostructures. Our findings provide a deep understanding of CsPbI 3 /MS 2 heterostructures and suggest an effective way to improve the performance of perovskite optoelectronic devices, such as radiation detection.