The influence of strain on the properties of the FAPbI₃ photoactive phase

Here the optoelectronic, defect, and mechanical properties of strain-induced α-FAPbI₃ are investigated. The strain range of -5% to 5% induces bandgap variation from 0.98 eV to 1.91 eV, and the strain along the [111] crystal orientation maintains a direct bandgap, while the strain along the [100] and [110] orientations may transform the direct bandgap into an indirect bandgap. Compressive strain shifts the iodine vacancy energy from the deep level to a shallow one, which stabilizes the photoactive material by elevating the α-FAPbI₃ phase. The [111] orientation under -2% strain achieves a photoelectric conversion efficiency (PCE) of 31.9%, providing an optimized strategy for designing efficient and stable perovskite solar cells.