Interface engineering at electron transport/perovskite layers using wetting mesoporous titanium dioxide to fabricate efficient and stable perovskite solar cells

The unique photovoltaic features of perovskites have encouraged researchers to use them as an active layer for solar cell applications. Recombination issue at electron transport layer (ETL)/perovskite interface is one of the reasons for performance reduction in perovskite solar cells (PSCs) and need to address. Hereof, we developed a simple and cheap method to modify this interface by wetting the mesoporous TiO2 ETL using mixed solvents of γ-butyrolactone (GBL) and dimethyl sulfoxide (DMSO). With optimization of the ratio of GBL and DMSO, our results showed a smoother perovskite layer with fewer pinholes on it. In addition, ETL wetting affected perovskite grain sizes and passivated grain boundaries in it. The mentioned reasons reduced carriers' trap centers in the perovskite film and suppressed charge recombination processes within PSCs. The improved crystalline properties of the modified perovskite layer facilitate electron extraction at ETL/perovskite interface and reduce charge accumulation, which brings a champion efficiency of 18.72% for the treated devices higher than that of 15.21% for the untreated devices. Moreover, due to the boosted hydrophobic property of the modified perovskite film, the stability behavior of the related PSCs was improved remarkably.