Recovering MAPbI₃-based Perovskite films from water-caused permanent degradations by dipping in MAI solution

The development of organic/inorganic halide perovskite solar cells (PSCs) has grown rapidly and the highest efficiency of the devices has recently reached 23.3%. However, the relatively low stability of PSCs is impeding them from commercialization, the standard of which is very hard to achieve. To repair the exhausted perovskite is a relatively convenient way to commercialization. Here, perovskite films can be recovered by a simple method, which can be used to repair the perovskite films degraded by water. Via the repairing process, we observed the PbI₂ residues decomposed from perovskite by water were transformed into CH₃NH₃PbI₃ again, which gives rise to remarkably boosted optical properties, drastically improving film morphology and largely suppressing pinholes. Furthermore, perovskite degrades when meeting with polar solvents, which severely restricts the selections of hole transporting materials (HTMs) on the top of perovskite layers to semiconductors that are soluble or dispersible in low-polarity solvents, if the most popular electron transport materials like TiO₂ and SnO ₂ must be used, which can only be used below the perovskite layer. The post-treatment method we introduced can also be used to repair the decomposed perovskite to enrich HTMs families on the top of perovskite layers. PEDOT:PSS/water suspension was used to form a hole transporting layer in this work as an example.