Effects of RbI doping on perovskite film and photovoltaic performance

Perovskite solar cells are brought into sharp focus by their high-power conversion efficiencies and low costs. However, their photovoltaic performances are severely limited by the defects of perovskite films. In this study, we composed perovskite films with a two-step method and doped RbI into the precursor solution. The morphologies of perovskite films were measured with scanning electron microscope (SEM), ultraviolet visible absorption spectroscopy (UV-Vis), Xray diffraction (XRD) and photoluminescence spectroscopy (PL), and photovoltaic properties were determined with solar simulator. The effects of different RbI concentrations on film morphology and photovoltaic performance of the perovskite films were investigated in this work. Results show that doping with RbI of low-concentration is instrumental to the grain size and film morphology and enhances the absorbance of 400-580 nm spectrum. However, high-concentration doping is detrimental to the perovskite film, resulting in more holes on surface and diminished absorbance. The best doping concentration of RbI is 10 mg/mL. Comparing with undoped perovskite film, the grain size increased from 500-1000 nm to 1-2 μm, and short-circuit current density is increased from 23.48 mA/cm² to 23.73 mA/cm², with 10 mg/mL RbI doped into the precursor solution. This study not only helps optimize the perovskite film morphology, but also help improve photovoltaic performance of perovskite solar cells.