Bifunctional Interfacial Modification Engineering with Biomimetic Perfluoro-Copolymer-Enabled High-Efficiency and Moisture-Resistant Perovskite Solar Cells

In recent years, interfacial technology encompassing attributes such as defect passivation and stability enhancement of perovskite solar cells (PSCs) has captivated the solar research fraternity with their power conversion efficiency (PCE) being as high as 25.5%. In accordance with the theory of compounding two functional groups integrally into a single structure under relatively moderate formation conditions, this paper presents an efficacious interfacial passivation modification strategy for PSCs with well-controlled morphologies and passivated charged surface states using a bidentate ligand perfluorocarbon copolymer (PFOMA). The strategy involves self-assembly of biomimetic PFOMA on a perovskite surface due to the coordination binding between the catecholic OH groups of PFOMA and Pb²⁺. The time-resolved photoluminescence measurements demonstrated that the effective passivation of catecholic OH groups benefits from the inhibition of the photogenerated carrier recombination. Furthermore, the long fluorocarbon alkyl chains of PFOMA bestow the perovskite surface with higher resistance against moisture. Hence, the resulting PFOMA-modified PSC can accomplish an above-average efficiency of about 20.66% (with an average PCE of 19.71%) with a notable increment in the open-circuit voltage of about 40 mV compared to the control voltage (1.12 mV). Particularly, the PFOMA-modified PSC exhibits a remarkable enhancement in the moisture stability factor under a relative humidity of 70 ± 5%, retaining >90% of their initial efficacies along with considerably upgraded device performance (an average PCE of 19.71% and a champion device PCE of 20.66% were achieved) and an enhanced moisture stability factor even under a relative humidity of 70 ± 5%. The highly proficient passivation strategy demonstrated in this work can help the future exploration of this function-oriented synthesis strategy and can pave the path for the universal application of PSCs employing the modification of polymers and more organic species.