Spray-Deposited, Virus-Templated SnO₂ Mesoporous Electron Transport Layer for High-Efficiency, Sequential-Deposited Perovskite Solar Cells

In recent years, researchers have developed spray deposition technology to fabricate tin oxide electron transport layer (ETL) with the aim of manufacturing high-efficiency, large-area perovskite solar cell (PSC). However, the power conversion efficiency (PCE) of PSC based on sprayed SnO₂ ETL remains inferior to that of the spin-coated SnO₂ ETL. Herein, the combined use of spray deposition and genetically engineered M13 bacteriophages for the deposition of M13-SnO₂ biohybrid ETL over large-area (62.5 cm²) substrates is demonstrated. The spray-deposited M13-SnO₂ ETLs exhibit mesoporous morphologies with >85% transmittance in UV–vis region. Through the use of M13-SnO₂ ETL, the sequential-deposited PSCs achieve a maximum PCE of ≈22.1%. The improved performance of the PSC is attributable to the mesoporous morphology of M13-SnO₂ ETL that facilitates the growth of larger perovskite grains. The PSCs based on M13-SnO₂ ETLs also display highly consistent photovoltaic performance which manifests the excellent scalability of the spraying process. Furthermore, M13-SnO₂-based PSCs exhibit higher ambient stability compared to the SnO₂-based PSCs, showing that the use of M13 bacteriophage is incredibly beneficial to both the efficiency and stability of PSCs.