An interlayer with strong Pb-Cl bond delivers ultra-violet-filter-free, efficient and photostable perovskite solar cells

Summary The inorganic metal oxides (IMOs), including titanium dioxide (TiO2) and tin dioxide (SnO2) inevitably induce decomposition of perovskite under ultra-violet (UV) illumination due to their photocatalytic activity and the use of a UV filter will add extra cost and reduce the effective power output. Here, we firstly reveal that the weak Pb-I bond in I-based perovskite is prone to breakage under UV photocatalysis, leading to serious degradation of SnO2/perovskite interface. We introduce a chlorine-rich mixed-halide perovskite interlayer (ClMPI), which possesses an excellent tolerance to photocatalysis due to the strong Pb-Cl bond, between the SnO2 and I-based perovskite. The ClMPI-based device achieves an enhanced efficiency of up to 21.01% (certified 20.17%). Most importantly, the resultant devices can maintain >94% of their initial performance after 180 h under outdoor solar irradiation, >80% after 500 h under UV irradiation and 500 h under continuous full spectrum illumination at their maximum power points.