An efficient, flexible perovskite solar module exceeding 8% prepared with an ultrafast PbI₂ deposition rate

Large-area, pinhole-free CH₃NH₃PbI₃ perovskite thin films were successfully fabricated on 5 cm × 5 cm flexible indium tin oxide coated polyethylene naphthalate (ITO-PEN) substrates through a sequential evaporation/spin-coating deposition method in this research. The influence of the rate-controlled evaporation of PbI₂ films on the quality of the perovskite layer and the final performance of the planar-structured perovskite solar cells were investigated. An ultrafast evaporation rate of 20 Å s^-1 was found to be most beneficial for the conversion of PbI₂ to CH₃NH₃PbI₃ perovskite. Based on this high-quality CH₃NH₃PbI₃ film, a resultant flexible perovskite solar sub-module (active area of 16 cm²) with a power conversion efficiency of more than 8% and a 1.2 cm² flexible perovskite solar cell with a power conversion efficiency of 12.7% were obtained.