Chemical Decoration of Perovskites by Nickel Oxide Doping for Efficient and Stable Perovskite Solar Cells

Crystal engineering of CH₃NH₃PbI_{3- x}Cl _x perovskite films through modification by decoration with p-type semiconductor materials was proposed as an efficient method for obtaining good-quality crystalline films. A simple method is demonstrated to improve the quality of perovskite films by adding nickel oxide (NiO _x) nanoparticles into the precursor solution. The addition of NiO _x brings about high-quality crystals and convenient photo-generated charge transport with reduced defect density owing to efficient control of the preferred nucleation and crystal growth. The sufficient contact between CH₃NH₃PbI_{3- x}Cl _x-NiO _x and the electron-transport layer can contribute to photo-generated carrier lifetime and transport through the optimized interface. Moreover, it is demonstrated that a strong chemical bonding interaction between MAPbI_{3- x}Cl _x and NiO _x could protect perovskite materials from oxygen and humidity corrosion, showing remarkable stability holding ∼81% of the initial power conversion efficiency (PCE) after 50 days. The device with the best PCE of 19.34% is achieved because of the improved short-circuit current from 22.23 to 23.01 mA cm^-2 and fill factor from 68.97 to 75.06%. The results certify that this p-type charge transport material decoration method for the optimization of perovskite films is an efficient way to optimize the performance.