A zwitterionic polymer as an interfacial layer for efficient and stable perovskite solar cells

Perovskite solar cells have been rapidly developed in the past ten years. It was demonstrated that the interfacial layer plays an important role in device performance of perovskite solar cells. In this study, we report utilization of a photoinitiation-crosslinked zwitterionic polymer, namely dextran with carboxybetaine modified by methacrylate (Dex-CB-MA), as an interfacial layer to improve the film morphology of the CH₃NH₃PbI₃ photoactive layer and the interfacial contact between the poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) hole extraction layer and CH₃NH₃PbI₃ photoactive layer. It is found that the Dex-CB-MA thin layer forms a better band alignment between the PEDOT:PSS hole extraction layer and CH₃NH₃PbI₃ photoactive layer, and improves the crystallization of the CH₃NH₃PbI₃ photoactive layer, resulting in efficient charge carrier transport. As a result, perovskite solar cells with the PEDOT:PSS/Dex-CB-MA hole extraction layer exhibit more than 30% enhancement in efficiency and dramatically boosted stability as compared with that with the PEDOT:PSS hole extraction layer. Our studies provide an effective and facile way to fabricate stable perovskite solar cells with high power conversion efficiency.