Naphthalene Diimide‐Modified SnO2 Enabling Low‐Temperature Processing for Efficient ITO‐Free Flexible Perovskite Solar Cells

A low-cost and indium-tin-oxide (ITO)-free electrode-based flexible perovskite solar cell (PSC) that can be fabricated by roll-to-roll processing shall be developed for successful commercialization. High processing temperatures present a challenge for the PSC fabrication on flexible substrates. The most efficient planar n-i-p PSC structures, which utilize a metal oxide as an electron transport layer (ETL), necessitate high annealing temperatures. In addition, the device performance deteriorates owing to the migration of halogen ions, which causes the oxidation of the metal electrodes. These drawbacks conflict with the development of highly efficient flexible PSCs fabricated on ITO-free transparent electrodes. Herein, an efficient ETL material that enables low-temperature processing is presented. Tin dioxide (SnO