Interfacial electrostatic repulsion inhibits iodide ion migration for enhancing reverse-bias stability of perovskite solar cells

The perovskite solar cells (PSCs) achieve notable advances in stability under humidity, light, and heat stress. However, PSCs are still susceptible to reverse-bias degradation, mainly due to the inevitable iodide ions migration. Herein, we reveal the irreversible cross-layer migration of iodide ion (I^-) within PSCs under reverse bias, which contributes to the device performance failure. Further, we innovatively construct an electrostatic repulsion with I^- at the perovskite interface, which can inhibit I^- cross-layer migration under reverse bias in a nonbonding manner. Besides, the TFMS capable of blocking the hole injection can reduce the interface I^- oxidation under reverse bias. The modified PSCs deliver efficiencies of 25.80% with TiO₂ as the electron transport layer (ETL) and 26.21% (certification of 26.09%) with SnO₂ as the ETL. More importantly, the device exhibit an enhanced reverse-bias stability by maintaining >80% of initial efficiency after 25 bias aging cycles (0 V/-1 V/0 V, each stage lasts for 12 hours). Our work provides a route to inhibit ion migration in PSCs and other perovskite-based devices through a novel interaction of electrostatic repulsion.