Multi‐cation Hybrid Perovskite Solar Cells

Perovskite photovoltaics have risen to prominence over the last decade as perovskite solar cell efficiencies have risen from 3.9% in 2009 to over 25.2% in 2020. High efficiency hybrid organic—inorganic perovskites typically include one or more A-site organic cations such as methylammonium or formamidinium but can also include inorganic cations, with cesium being the most common additive. Multi-cation perovskites are considered to be those which include more than one of these A-site cations and can be either lead- or tin-based. Lead-based multi-cation perovskites have emerged as the best performing perovskites for solar cell application to date. Formamidinium-based perovskites have shown exceptional efficiencies when combined with a smaller amount of methylammonium and/or cesium and have improved stabilities when compared to single-cation perovskites. Further additions to the cation cascade such as smaller alkali cations like potassium or rubidium have shown promising benefits, although the inclusion of these cations in the perovskite structure has been an area of debate among researchers