Formation of Metal Cation/Oxidized Pyridine Complexes-Based Bifunctional Interfacial Layer for Fabrication of Highly Efficient and Reproducible Perovskite Solar Cells

Abstract

Interfacial engineering of perovskite solar cells (PSCs) has been a core process for enhancing their power conversion efficiencies (PCEs) and environmental stability. Particularly, polymeric passivation of a metal oxide-electron transport layer (ETL) not only leads to a reduction in its surface defects but also improves the morphology of perovskite. However, the dissolution of the passivation layers by dimethylformamide (DMF) in a perovskite solution can cause a significant drop in the PCE and reproducibility of devices. Herein, oxidized poly (4-vinylpyridine) (O-P4VP) is used as a bifunctional passivation layer. The O-P4VP layers are completely insoluble in DMF, which accompanies the highly reproducible deposition of perovskites without damaging the layers. Furthermore, based on metal-pyridine complexation, oxygen vacancies on the surface of the SnO2 ETLs are passivated with the O-P4VP layers, and the perovskite grains become enlarged by the controlled nucleation and growth rate. The synergetic effects of interfacial passivation present deeper energy levels of the ETL and a prolonged photoluminescence lifetime of the perovskites. The resulting PCE jumps from 19.05% to 21.11% with respect to the pristine device, and the value is retained for 720 h under 1 sun illumination.