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.