Ultrathin Glass-based Perovskite Solar Cells Employing Bilayer Electron Transport Layer

Abstract In recent studies, flexible perovskite solar cells (PSCs) have exhibited high power conversion efficiency (PCE) coupled with remarkable mechanical stability. However, the conventional polymer substrates used in flexible PSCs possess high permeability to moisture and oxygen, leading to the rapid degradation of perovskite materials. In this work, we address these issues by employing ultrathin glass (UTG) substrates, which provide moisture impermeability while retaining flexibility. Additionally, we introduce a strategically designed SnO₂/TiO₂ bilayer as the electron transport layer (ETL). Our results reveal that PSCs incorporating the bilayer ETL achieve higher PCE than those with a monolayer ETL on conventional glass and UTG substrates. Furthermore, moisture permeability tests demonstrate that PSCs based on UTG substrates sustain their PCE over time, compared to their polymer-based counterparts. These results imply that UTG substrates, combined with a SnO₂/TiO₂ bilayer ETL, offer a promising solution for developing durable, high-performance, flexible PSCs suitable for long-term applications.