Sequential Deposition of Diluted Aqueous SnO2 Dispersion for Perovskite Solar Cells

The widespread use of tin dioxide (SnO 2 ) thin films as electron transport layer (ETL) of perovskite solar cells (PSCs) has been facilitated by commercial SnO 2 nanocolloid dispersion. Nevertheless, challenges such as nanoparticle agglomeration have emerged, impacting film quality and interface properties critical for PSC performance. Herein, the efficacy of sequential, multistep spin‐coating of repeatedly diluted SnO 2 aqueous suspension as a simple and effective approach to enhance ETL properties is explored. Through systematic experiments using dynamic light scattering, cyclic voltammetry, optical spectroscopy, and photoconductivity, it is demonstrated that the sequential deposition significantly improves the flatness and coverage of SnO 2 , leading to improved electron transport and transfer from a perovskite layer. Such a synergetic effect enables to fabricate lead iodide PSC (FAPbI 3 , FA: formamidinium) with a power conversion efficiency of 22.99% compared to 20.48% for the conventional 1‐step SnO 2 layer. The findings underscore the potential of sequential SnO 2 deposition as a promising technique for robust SnO 2 films of photoelectric conversion devices.