Role of Mixed-Cation Perovskites in Hole Conductor-Free Perovskite Solar Cells

In perovskite solar cells, mixed-cation perovskites offer high power conversion efficiencies due to the diverse A+ cations. In these cells, the perovskite is sandwiched between electron-transport and hole-transport layers (HTL). This study presents mono- and mixed-cation perovskites in HTL-free cells: monocation (MAPbI(3), FAPbI(3)) and mixed cation (MA(0.8)FA(0.2)PbI(3), FA(0.8)MA(0.2)PbI(3)). Surprisingly, monocation perovskites performed better than mixed-cation perovskites in HTL-free cells due to superior hole mobility and p-type behavior, while mixed-cation perovskites work better in n-i-p and p-i-n cells. These findings highlight the electronic differences for various types of perovskite, impacting the commercialization of perovskite solar cells.