Abstract
Addition of lead chloride (PbCl2) 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 (PbI2) platelet atop the film, which adversely affects carrier transport. To eliminate the negative effect of PbI2 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, PbI2 platelets are converted into cesium lead halide perovskites (CsPbX3) through reaction with Cs and halide present in the original perovskite Cs0.22FA0.78Pb(I0.85Br0.15)3. An efficiency enhancement of (>10%) is achieved by FAI treatment, which does not require fast solvent removal or nitrogen (N2) atmospheres, indicating that FAI blade coating is an effective and straightforward method for the post-treatment of excess PbI2.
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