An Interface Strategy on SnO2 for Stable Planar Perovskite Solar Cells

Abstract

Defects and band shifts at the heterogeneous interface between the perovskite layer and the charge transport layer are two important problems that hinder the efficiency of photoelectric conversion and the stability of devices. Considering these issues, an interface engineering to reinforce the operation stability of FACsPbI3 perovskite solar cells (PSCs) by the introduction of a multifunctional ligand 2-carboxyphenyl ethyl phosphate (CEPPA) modification layer between the electron transport layer and the perovskite layer is presented. It demonstrates that CEPPA adsorbs on the substrate surface to passivate the oxygen vacancy defects and effectively reduce the defect states on SnO2 films. On the other hand, the optimized arrangement of energy levels leads to better electron extraction and transport. Eventually, the power conversion efficiency (PCE) of the FACsPbI3 device increases from 16.33% to 17.78%. Moreover, compared with unmodified SnO2, the unpackaged devices with CEPPA-modified SnO2 show better phase stability and moisture stability. Unpackaged devices retain more than 80% of their initial PCE after 500 h of aging. Herein, a further perspective for the analysis and development of buried interfaces and an effective approach for better improving the function and stability of PSCs are presented.