Probing Band-Alignment at the Interface of 3D/2D Perovskites for Solar Cell Applications

In this report, the effect of interfacial band-alignment in 3D/2D perovskite heterostructures on the performance of solar cells has been studied. The heterostructures have emerged as a preferred approach to slow down the degradation of 3D perovskites. We have incorporated three different organic spacers, namely butylammonium (BA+), phenethylammonium (PEA+), and ethanolamine (EA+), in forming the 2D perovskite layer over the top of a 3D triple-cation halide perovskite. The power conversion efficiency has been found to depend on the 2D perovskite. The band-energies of the 3D and the 2D perovskites, derived from scanning tunneling spectroscopy and Kelvin probe force microscopy, have showed that the EA+-based capping layer forms a type-II band-alignment at the 3D/2D interface and thereby facilitates charge separation. Our work depicts the necessity of probing the interfacial band-alignment while fabricating solar cells based on 3D/2D perovskites.