Using Multifunctional Molecular ‘Glue’ for Bilateral Interface Engineering to Stabilize Perovskite/SnO₂ Layers

Single junction perovskite solar cells (PSCs) have surpassed a photoelectric conversion efficiency (PCE) of 27%. However, inevitable interface defects from the preparation process have emerged as notorious barrier to further enhancing performance. In this study, we introduce the L-isoleucine (L-lle) to modify the buried interface between tin dioxide (SnO₂) and perovskite in PSCs. The oxygen atoms on the carboxyl group (-COOH) of L-lle migrate upward and chemically bond with the uncoordinated lead ions on the perovskite surface, effectively anchoring the displaced lead ions. Concurrently, the downward movement facilitates esterification reaction with the hydroxyl groups (-OH) on the surface of SnO₂, which enhances molecular cross-linking, expands interface contact, and improves the stability of L-lle at the buried interface. The efficiency of PSC devices based on L-lle exhibit a significantly higher efficiency than that of control devices (23.54%), reaching 26.15%. Furthermore, after 1200 h of long-term stability testing, the modified device can retain 92% of its initial efficiency, demonstrating outstanding operational stability.