Enhanced photovoltaic properties of 2D organic perovskite FA0.5MA0.5SnI3via crystal orientation and exposed facets.

Sn-based perovskite is considered to be the most promising environmentally friendly alternative material because of its low toxicity and photoelectric properties similar to lead-based perovskite. However, its inherent instability and low efficiency under operating conditions pose significant challenges for commercial application. To address these drawbacks, a novel strategy involving hybrid FA/MA cation engineering has been implemented in Sn-based perovskite systems, and the best organic perovskite FA0.5MA0.5SnI3 was selected according to its photoelectric properties and stability. By simulating physical peeling, 10 kinds of 2D organic perovskite FA0.5MA0.5SnI3 with various crystal orientations and exposed facets were obtained. Based on their cohesive energy, thermodynamic stability, and cleavage energy, four stable 2D organic perovskites FA0.5MA0.5SnI3 were identified. It was found that when the exposed facets contain FA and MA ion hybridization, it can enhance stability, increase the bandgap, and raise the Fermi level. The effect of exposed facets on band gap is significantly greater than that of crystal orientation. The absorption spectrum shows that the light absorption is more significantly affected by exposed facets than the crystal orientation. Through device simulation, the J-V curve, fill factor, quantum efficiency curve, and photoelectric conversion efficiency (PCE) are more significantly affected by exposed facets than the crystal orientation. The PCE of 2D organic perovskite FA0.5MA0.5SnI3 with [110]-oriented FAI facets was 21.317%. This study elucidates the microscopic mechanism of crystal orientation and MA/FA ion hybridization on exposed facets for the change of photoelectric properties of 2D organic perovskite FA0.5MA0.5SnI3, and accelerates the exploration of high-performance perovskite photovoltaic devices through theoretical research. The potential of crystal orientation and exposed facet engineering in improving photoelectric performance and expanding the applications in the photoelectric field is emphasized.