High-performance photovoltaic application of the 2D all-inorganic Ruddlesden–Popper perovskite heterostructure Cs2PbI2Cl2/MAPbI3

Abstract

The three-dimensional (3D) organic–inorganic halide perovskite MAPbI₃ has excellent light-harvesting properties but is unstable. However, the newly synthesized two-dimensional (2D) all-inorganic Ruddlesden–Popper (RP) perovskite Cs₂PbI₂Cl₂ has superior stability but adverse photoelectric properties. Therefore, constructing a 2D Cs₂PbI₂Cl₂/3D MAPbI₃ heterostructure is expected to combine the superstability of the 2D material and the high efficiency of the 3D one. The photoelectric properties and charge transfer of 2D Cs₂PbI₂Cl₂/3D MAPbI₃ heterostructures are investigated using density functional theory, where MAPbI₃ has two kinds of contacting interfaces, i.e., MAI and PbI interfaces. The band gaps of 2D/MAI and 2D/PbI heterostructures are 1.52 eV and 1.40 eV, smaller than those of the free-standing materials (2D ∼ 2.50 eV, MAI ∼ 1.77 eV, and PbI ∼ 1.73 eV), which can broaden the light absorption spectrum. Moreover, the 2D/3D heterostructures are typical type-II heterostructures, which is beneficial to facilitate the separation of carriers for increasing the photoelectric conversion. Interestingly, due to the work function difference (2D ∼ 4.97 eV, MAI ∼ 3.57 eV, and PbI ∼ 5.49 eV), the charge transfer directions of the 2D/MAI and 2D/PbI heterostructures are completely opposite, which shows that interface engineering to impose a consistent interface termination is needed to obtain good performance for solar cells. These results demonstrate that constructing 2D Cs₂PbI₂Cl₂ and 3D MAPbI₃ heterostructures by interfacial engineering is a potential strategy to improve the performance of perovskite solar cells (PSCs).