Continuous Modification of Perovskite Film by a Eu Complex to Fabricate the Thermal and UV-Light-Stable Solar Cells

Perovskite solar cells (PSCs) with simple and low-cost processability have shown promising photovoltaic performances. However, internal defects, external UV light, and heat sensitivity are principal obstacles on their way toward commercialization. Herein, we prepare an Eu complex and directly dope it into the perovskite precursor as a UV filter to decrease the photodegradation of PSCs. The formation of hydrogen bonds between the organic cation of perovskite and the -CF₃ in the Eu complex could restrain the escape of organic cations under heating. The Eu complex acts as a redox shuttle to reduce metallic lead (Pb⁰) and iodine (I⁰) defects when the PSCs have a long-time operation. Additionally, the ligand-containing aromatic rings could reduce the trace amount of I⁰ existing as electronic defects in perovskites and together with the long alkyl chain retard the moisture immersion into the PSCs. The best efficiency of PSCs modified by the Eu complex improves up to 20.9%. The excellent thermal stability and UV-light resistance are also realized. This strategy provides a method to design a passivator which continuously modifies the imperfections and inhibits the chemical chain reactions in perovskite film, thereby enhancing the performance and stability of PSCs.