Preparation of Micron-sized Methylamine-PbCl₃ perovskite grains by controlling phase transition engineering for selective Ultraviolet-harvesting transparent photovoltaics

Selective ultraviolet-harvesting transparent perovskite solar cells (T-PSCs) have attracted great interest because of their high transmittance and unique photovoltaic properties, especially in the fields of smart windows for power generation and building glass. However, owing to the unsatisfactory solubility of PbCl₂ in most conventional solvents, preparing transparent methylammonium lead chloride (MAPbCl₃) films with high quality and sufficient thickness by conventional methods poses a substantial challenge for their application deployment in T-PSCs. In this work, two novel strategies based on an ion-exchange procedure for controlling phase transition engineering (CPTE) are proposed. For CPTE-2, an optimized cubic phase MAPbCl₃ film with a large grain size and high full coverage is prepared by transforming the tetragonal phase MAPbI₃ precursor into the cubic phase MAPbCl₃. Establishing relevant models based on crystal parameters investigates the formation mechanism of this high-quality MAPbCl₃ film. Accordingly, the resultant T-PSCs exhibit remarkable film quality and micron-sized grains and reach an optimum efficiency of 0.33% (J_SC = 0.66 mA cm⁻², V_OC = 1.14 V, and FF = 43.72%).