Effective approach for reducing the migration of ions and improving the stability of organic–inorganic perovskite solar cells

Highlights: • Reducing the migration of ions and improving the stability of solar cells. • The organic cation migration effects of perovskites were investigated. • FA cations exhibit high activation energy in the mixed FMRCPbI perovskite. • The diffusion of FA cations in FMRCPbI mixed perovskite is suppressed. • FMRCPbI mixed perovskite may be a new generation perovskites for photovoltaics. The power conversion efficiency of organic–inorganic halide perovskite solar cells has exceeded 20% because of the outstanding properties of perovskite materials. However, the practical application of perovskite solar cells is hindered by their poor stability, which is related to the ion transport properties of perovskite materials. In this study, we explore an effective approach for reducing the migration of ions and improving the stability of solar cells by using mixed organic–inorganic perovskites. The structural and electronic properties of the mixed halide perovskites, namely, FMRCPbI and FMRCPbI, with various cation vacancies ($V_{\text{MA}}^{\text{'}}$, $V_{\text{FA}}^{\text{'}}$, $V_{\text{Cs}}^{\text{'}}$, and $V_{\text{Rb}}^{\text{'}}$) and the organic cation migration effects of MAPbI₃, FAPbI₃, and mixed FMRCPbI₃ perovskites were investigated using first-principles method. FA cations exhibit high activation energy in the mixed FMRCPbI perovskite, suggesting that the diffusion of FA cations in FMRCPbI mixed perovskite is suppressed. In addition, radiation recombination is slightly small in FMRCPbI with a high concentration of cation vacancies due to the absence of energy levels of vacancy defects in the band gap. With its relatively low recombination loss and direct band gap with high absorption coefficient and high thermal stability, FMRCPbI mixed perovskite may be a new generation of highly efficient and emissive perovskites for photovoltaics and photoemission applications.