Effect of Sr substitution on the air-stability of perovskite solar cells

By using a two-step spin-coating method, 10 mol% SrI 2 and 10 mol% SrCl 2 -substituted perovskite films were synthesized and utilized to construct mesoscopic perovskite solar cells (PSCs), respectively. The influences of Sr substitutions on the humidity and thermal stability of PSCs were systematically investigated. It is indicated that both 10 mol% SrI 2 substitution and 10 mol% SrCl 2 substitution can enhance the power conversion efficiency (PCE) of PSC to more than 15%. The 10 mol% SrCl 2 substitution can improve the humidity resistance of perovskite films, which is conducive to inhibiting the increase of perovskite's defect density caused by humidity. After storing at 20 ± 5 °C, 30 ± 5%RH for 21 d, the 10 mol% SrCl 2 -substituted PSC can still maintain 84% of the initial efficiency. However, the 10 mol% SrI 2 -substituted PSC exhibits a strong humidity sensitivity, which results in the increase of series resistance and the decrease of recombination impedance, thus making the PCE decrease to less than 20% of the initial value after storing at 20 ± 5 °C, 30 ± 5%RH for 21 d. As for the thermal stability of PSCs, both the 10 mol% SrI 2 and 10 mol% SrCl 2 -substituted perovskite films exhibit a certain thermal resistance. After 18 thermal cycles, both the 10 mol% SrI 2 and 10 mol% SrCl 2 -substituted PSCs can maintain over 90% of the initial PCEs.