High Performing Inverted Flexible Perovskite Solar Cells via Solution Phase Deposition of Yttrium-Doped SnO₂ Directly on Perovskite

Solution processing of flexible perovskite solar cells (f-PSCs) provides an avenue for scalable, high-throughput printing of lightweight, scalable, and cost-effective flexible solar cells. However, the deposition of fully solution-processed metal oxide charge transport layers on perovskites has been limited by solvent incompatibilities and high processing temperatures for metal oxide nanoparticles. In this study, we present high-performance, inverted f-PSCs from the direct deposition of yttrium-doped SnO 2 nanoparticles functionalized with acetate on top of perovskite as an ink in anhydrous ethanol via blade coating. Yttrium doping improved device performance by improving the charge extraction with a decreased series resistance leading to improvements in the open-circuit voltage and fill factor. The champion power conversion efficiency for 0.1 cm 2 devices increased from 14.3% for undoped SnO 2 to 16.5% with 2% Y:SnO 2 doping, which is unprecedented for f-PSCs on ITO-PET substrates employing SnO 2 as an ETL.