LAUSR

Abstract Hybrid perovskite solar cell (PSC) has attracted extensive research interest due to its rapid increase in efficiency, regarding as one of the most promising candidates for the next-generation photovoltaic technology. The certified power conversion efficiency of the devices based on formamidinium lead iodide (FAPbI3) perovskite has reached 25.5%, approaching the record of monocrystalline silicon solar cells. Unfortunately, the black α-phase FAPbI3 materials can spontaneously transform to non-optically active δ-phase at room temperature, which greatly hinder their photovoltaic application. In order to overcome this problem, various strategies, especially introducing methylammonium (MA+), caesium (Cs+) and bromide (Br-) ions into the materials, have been widely adopted. However, MA+ can largely reduce the thermal stability of the materials. Furthermore, the introduction of Br- can enlarge the materials’ bandgap, resulting in a reduced theoretical efficiency. Keeping these in mind, developing the strategies which without using MA+ and Br- is the inevitable trend. Here, we focus on the recent progresses of stabilizing α FAPbI3 without employing MA+ and Br-, and discuss the advantages of inorganic ions doping and dimensionality engineering to stabilized α FAPbI3. Meanwhile, in order to deeply understand the relationship between the semiconducting properties and device performance of the corresponding materials, we then summarize several significant strategies to suppress the non-radiation recombination, such as interface modification and trap passivation. Finally, we propose to develop more effective ‘A-site’ alternatives to stabilize α FAPbI3, which is expected to achieve high-efficient PSCs with long-term stability, facilitating its commercialization process.