Quantum Confinement Breaking: Orbital Coupling in 2D Ruddlesden-Popper Perovskites Enables Efficient Solar Cells

摘要

2D Ruddlesden-Popper perovskites have become emerging photovoltaicmaterials due to their intrinsic structure stability. Here, a concept of“quantum confinement breaking” in 2D perovskites is proposed using organicsemiconductor spacers with suitable energy levels based on theoreticalcalculation and experimental results. An interesting finding is that there isintensive orbital coupling between the bithiophenemethylammonium(BThMA) spacer and adjacent inorganic layers in (BThMA)_2PbI_4, resulting inthe breaking of the multiple quantum well structure. In comparison, no orbitalinteractions exist in (BPhMA)_2PbI_4 due to the wide bandgap of thebiphenemethylammonium (BPhMA) spacer. Benefitting from the improvedfilm quality, increased dielectric constant, and reduced binding energy, the(BThMA)_2MA_(n?1)Pb_nI_(3n+1) (n = 5) perovskite-based device displays anoutstanding power conversion efficiency (PCE) of 18.05, which is muchhigher than that of the BPhMA-based device (PCE = 12.69) and among thebest efficiency in 2D PSCs based on long conjugated spacers. The resultsprovide an important implication for the effects of orbital interactions betweenorganic semiconductor spacers and the adjacent PbI_6~(4?) octahedron layer onthe performance of 2D perovskite solar cells and other optoelectronic devices.