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 Sn2+ is a current dilemma. Here, for the first time, the highly efficient Pb-Sn-Cu ternary PSCs are reported by partial replacing of PbI2 with SnI2 and CuBr2 . Sn2+ substitution results in a redshift of the absorption onset, whereas worsens the film quality. Interestingly, Cu2+ 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 Cu2+ passivation.