Organic - Inorganic hybrid lead iodide perovskite featuring zero dipole moment guanidinium cations: A theoretical analysis

Three-dimensional organic–inorganic lead iodide perovskites are potential photoconductive materials for solar cells. Nowadays, a high power conversion efficiency exceeding 20% can be achieved. However, perovskite solar cells are reported to suffer from a large hysteresis in the current–voltage curves. This may be attributed to the motion of organic cations with a permanent dipole moment in response to the applied electric field. Therefore, in order to suppress the hysteresis, organic cations that have a zero dipole moment and a molecular size well fitted to the lead iodide cavity are required. Using density functional theory calculations, we theoretically studied the thermodynamic stability and electronic properties of lead iodide perovskites with large guanidinium cations having a nearly zero dipole moment and compared the results with those predicted via the Goldschmidt tolerance factor. The properties of formamidinium–guanidinium (FA1–xGAxPbI3) intermediate alloys were also investigated.