Disulfide bond containing self-healing fullerene derivatized polyurethane as additive for achieving efficient and stable perovskite solar cells

Given their low bond binding energy, perovskite films are prone to phase decomposition under harsh environments, causing the inevitable degradation of the device performance and operational stability loss. Herein, a high electron mobility self-healing polymer (C60-PU) is synthesized by combining polyurethane with pendent fullerene to heal the crystallographic defects of perovskite. The introduction of fullerene prevents the serious energy disorder brought by the low mobility polymer in the perovskite film. Incorporating C60-PU into the perovskite films could enhance the crystallinity while passivating the grain boundary of the perovskite films. Hence, the unencapsulated device with C60-PU achieves a high efficiency of 21.36% with a notable FF value of 82.66% and an enhanced stability in ambient environment over 25 days. Moreover, the dynamic disulfide bonds in C60-PU can repair the perovskite film defects formed during operation, and the performance can be repaired by a simple heat treatment.