Advancements in perovskite solar cell efficiency through blade coating techniques and post-treatment optimization

Addition of lead chloride (PbCl 2 ) improves the crystallization kinetics of perovskites by suppressing the formation of δ-phase during large-area perovskite film fabrication. However, this addition results in formation and accumulation of lead iodide (PbI 2 ) platelet atop the film, which adversely affects carrier transport. To eliminate the negative effect of PbI 2 accumulation and simultaneously obtain a dense, mirror-like perovskite film, a post-treatment method involving blade coating formamidinium iodide (FAI) under air atmosphere is used. Instead of being washed away, as reported in literatures using spin coating process, PbI 2 platelets are converted into cesium lead halide perovskites (CsPbX 3 ) through reaction with Cs and halide present in the original perovskite Cs 0.22 FA 0.78 Pb(I 0.85 Br 0.15 ) 3 . An efficiency enhancement of (>10%) is achieved by FAI treatment, which does not require fast solvent removal or nitrogen (N 2 ) atmospheres, indicating that FAI blade coating is an effective and straightforward method for the post-treatment of excess PbI 2 .