Design of SnO2 Electron Transport Layer in Perovskite Solar Cells to Achieve 2000 h Stability Under 1 Sun Illumination and 85 °C

In order to realize both efficient and stable perovskite solar cells, designing electron transport layer (ETL) is of crucial importance to withstand constant light illumination and thermal stress while maintaining high charge extractability. Herein, commonly used SnO2 nanoparticle‐based ETL for perovskite solar cells is modified by ionic‐salt ammonium chloride (NH4Cl) and tin chloride dihydrate (SnCl2∙2H2O) as additives, which is easily fabricated by simple one‐step spin coating of single precursor solution. With the presence of these dual additives at the ETL, the crystallinity of the upper perovskite layer is clearly enhanced. Defect analyses on the devices suggest that these modifications can effectively passivate trap sites that reside within the ETL and at the perovskite interfaces with the carrier‐transport layers. As a result, the modified SnO2 ETL results in an improvement of device stability under thermal or light stress condition, maintaining over 80% of its initial efficiency after ≈2000 h storage under elevated temperature (85 °C) and after ≈2400 h of operation under 1 sun illumination.