Pb–Sn–Cu Ternary Organometallic Halide Perovskite Solar Cells

Exploiting organic/inorganic hybrid perovskite solar cells (PSCs) with reduced Pb content is very important for developing environment‐friendly photovoltaics. Utilizing of Pb–Sn alloying perovskite is considered as an efficient route to reduce the risk of ecosystem pollution. However, the trade‐off between device performance and Sn substitution ratio due to the instability of Sn 2+ is a current dilemma. Here, for the first time, the highly efficient Pb–Sn–Cu ternary PSCs are reported by partial replacing of PbI 2 with SnI 2 and CuBr 2 . Sn 2+ substitution results in a redshift of the absorption onset, whereas worsens the film quality. Interestingly, Cu 2+ introduction can passivate the trap sites at the crystal boundaries of Pb–Sn perovskites effectively. Consequently, a power conversion efficiency as high as 21.08% in inverted planar Pb–Sn–Cu ternary PSCs is approached. The finding opens a new route toward the fabrication of high efficiency Pb–Sn alloying perovskite solar cells by Cu 2+ passivation.