Two-Dimensional van der Waals Heterostructures Constructed via Perovskite (C4H9NH3)2XBr4 and Black Phosphorus.

Heterogeneous stacking of two-dimensional (2D) perovskites with other 2D materials is a very effective strategy for designing low-cost and high-performance photovoltaic and optoelectronic devices. The structural, electronic, and optical properties of distinctive all-2D M2XBr4-black phosphorus (BP) [M = (C4H9NH3)+; X = Pb2+, Sn2+, Ge2+] van der Waals (vdW) heterostructures have been studied by first-principle calculations. The M2SnBr4-BP and M2GeBr4-BP heterostructures show type-II band arrangement; however, the M2PbBr4-BP heterostructure exhibits type-I band arrangement. The energy level shift is ascribed to the difference of work function between M2XBr4 monolayer and BP monolayer, driving the movement of carriers spontaneously. Furthermore, the BP layers can enhance the light absorption of the total heterostructures, especially the M2GeBr4-BP heterostructure. These results indicate the all-2D perovskite and BP vdW heterostructures are competitive candidates for low-dimensional photovoltaic and optoelectronic applications.