Stable and efficient perovskite solar cells by discrete two-dimensional perovskites capped on the three-dimensional perovskites bilayer thin film

The combination of the three-dimensional (3D) perovskites and the two-dimensional (2D) perovskites to create the 2D/3D perovskites bilayer structure was demonstrated to be a facile way to realize stable and efficient perovskite solar cells (PSCs). In this study, we report stable and efficient PSCs based on the 2D/3D PEA2PbBr0.3I3.7/MAPbBr0.3I2.7 thin film, where PEA is phenethylammonium and MA is methylammonium (MA). Systematically studies demonstrate that the 2D PEA2PbBr0.3I3.7 crystals are discretely capped on the top of the 3D MAPbBr0.3I2.7 thin film. These discrete 2D PEA2PbBr0.3I3.7 crystals could improve water resistance due to the hydrophobic 2D PEA2PbBr0.3I3.7, but without sacrificing the optoelectronic properties of the 3D MAPbBr0.3I2.7. Moreover, the 2D MAPbBr0.3I3.7 crystals could elevate the build-in potential, suppress the interfacial charge carrier recombination, and reduce the dark current density of the PSCs based on the 2D/3D PEA2PbBr0.3I3.7/MAPbBr0.3I2.7 thin film. As a result, the PSCs based on the 2D/3D PEA2PbBr0.3I3.7/MAPbBr0.3I2.7 thin film exhibit over 23% power conversion efficiency and boosted stability. These results demonstrate that we have provided a facile way to engineer the 2D PEA2PbBr0.3I3.7 crystals on the surface of the 3D MAPbBr0.3I2.7 for approaching stable and efficient PSCs.