Polymers and interfacial modifiers for durable perovskite solar cells: a review

Abstract

This review focuses on the advancements in stability of perovskite solar cells under stress from ambient moisture, high temperatures, and UV light exposure. Moisture stability has been improved by utilizing several polymeric encapsulation methods, moisture-resistant hole transport layers (HTLs), CF₄ plasma treatments, and perovskite grain crosslinking. Fluorinated encapsulation methods have proven especially successful, producing cells that maintained their PCE after 75 days at 50% RH and 5 mW cm⁻² of UV radiation. Temperature destabilization has been hypothesized to occur as a result of perovskite phase transitions and the HTL dopant migration to the mesoporous TiO₂ surface. Temperature-sensitive perovskites have been stabilized by tuning the Goldschmidt tolerance factor and introducing thermally resistant HTLs embedded in a polymeric matrix with polycarbonate acting as an effective thermal insulating matrix. UV light instabilities have also been shown to occur due to the photocatalysis of TiO₂ and the TiO₂ perovskite interface. The introduction of a Sb₂S₃ buffer or CsBr clusters as interface modifiers can stabilize the interface of TiO₂ perovskite. Herein, we aim at highlighting the main processes that prevent perovskite degradation using polymers and interfacial modifiers.