Water‐Based Recycling Process of FTO/SnO2 Substrate for Sustainable Perovskite Solar Cell Technology

Abstract Fluorine‐doped tin oxide (FTO) substrate is an important and expensive component in perovskite solar cells (PSCs), which accounts for up to 40 % of a typical PSC raw material cost. In this study, we investigated the recyclability of SnO 2 /FTO in PSCs by washing the spent PSCs using different solvent such as dimethylformamide (DMF), dimethylsulfoxide (DMSO), acetone, water, and acetone/water mixture. Characterisation of properties of the SnO 2 /FTO substrates recovered from the PSC show the surface wettability of SnO 2 /FTO is largely unchanged with water washing while a higher hydrophobicity is obtained with organic solvent washing. Comparison of electronic properties of the SnO 2 /FTO substrate shows a downward shift of the conduction band by 180 meV with water washing, creating favourable energy alignment with adjacent perovskite for efficient interfacial charge injection. Consequently, PSCs using the water‐based recycled SnO 2 /FTO substrates produced a high power conversion efficiency (PCE) of 19.33 % which is comparable to the device using fresh SnO 2 /FTO substrate (PCE=19.85 %). Furthermore, we demonstrated that the water washing process could retain property of SnO 2 /FTO substrate for decent PSC performance up to four recycling cycles. This study opens new avenues towards recycling of valuable FTO substrates in PSCs for increased sustainability and cost‐effectiveness.