Flexible Perovskite Solar Cells with Enhanced Performance Based on a Void-Free Imbedded Interface via a Thin Layer of Mesoporous TiO₂

The interfacial contacts between the electron transport layer (ETL) and the perovskite film play a crucial role in high-performance perovskite solar cells (PSCs). Herein, we propose a method for depositing a low-temperature-processed mesoporous TiO2 (mp-TiO2) layer on the SnO2 ETL (bl-SnO2) with the flexible substrate to enhance the performance of the PSCs. This kind of mesoporous TiO2 layer can both improve the interfacial contact without voids in the imbedded interface and enhance the mechanical stability in the interface between TiO2 and perovskite. The upward growth of perovskite grains on the mesoporous TiO2 layer leads to a uniform grain size and prevents voids at the ETL/perovskite interface. This excellent interfacial contact is the foundation for the collection and transportation of photogenerated electrons. As a result, the efficient PSCs achieve a power conversion efficiency (PCE) of 19.90% with the additional mp-TiO2 layer on a flexible substrate. Furthermore, the unencapsulated flexible PSCs show enhanced storage stability and bending durability. This work paves the way for the fabrication of cost-effective and high-quality flexible PSCs with enhanced efficiency and mechanical stability.