Improvement of stability of ZnO/CH₃NH₃PbI₃ bilayer by aging step for preparing high-performance perovskite solar cells under ambient conditions

To date, most of fabricating processes of efficient perovskite solar cells (PSCs) have been carried out in high vacuum conditions or nitrogen protection atmosphere. Here we report a simple and novel strategy to fabricate efficient and stable ZnO-based PSCs. Firstly, ZnO nanoparticles were prepared by zinc acetate hydrolysis in methanol, and then the growth of methylamine lead iodide (CH₃NH₃PbI₃) crystal layer was realized by a two-step method. With aging treatment of ZnO film, high-quality ZnO/CH₃NH₃PbI₃ bilayer was obtained. Most importantly, the fabrication, measurement and store of solar cells in our processes were totally carried out under ambient conditions without a high vacuum or oxygen-free and water-free environment. A maximum efficiency of 9.4% was achieved. Moreover, the prepared devices exhibited promising stability at 30% humidity and 25 °C without any protection. We believe that the proposed strategy would push the applications of PSCs.