Stable and Efficient Pb–Ni Binary Metal Perovskite Solar Cells

Despite becoming a potential photovoltaic technology, perovskite solar cells (PSCs) are still subject to the instability and lead toxicity. Partial substitution in lead sites has been proven as a valid strategy to enhance perovskite film quality and stability toward low-toxicity and high-performance PSCs. Here, Pb was partially substituted Ni for MAPb_1–xNi_xI₃ (x = 0–0.5) films to improve the stability and reduce the toxicity in PSCs. The little Ni substitution induced high quality of perovskite films with large grains to reduce the trap-state density and improve the carrier lifetime in PSCs. The average power conversion efficiency (PCE) of the PSCs increased to 18.52% from 17.64%, and the maximum value achieved was 20.63%. Moreover, the Ni²⁺-doped perovskite films can remain crystalline with excellent stability after 1 year in the humid air (20–30% humidity), so that the PSCs can retain 86% of initial PCE after 500 h with long-term stability. With more substituted amount of 10% Ni, the PCE of PSCs can still be maintained at 14.04%. This work suggests that the balance between long stability and less toxicity by Ni substitution can be a valid approach for efficient and stable PSCs.