Impurity-healing interface engineering for efficient perovskite submodules

Abstract

One issue that always strands the scaling-up development of perovskite photovoltaics is the significant efficiency drop when enlarging the device area, which is caused by the inhomogeneous distribution of defected sites^1-3. In the narrow band gap formamidinium lead iodide (FAPbI₃), the native impurities of PbI₂ and δ-FAPbI₃ non-perovskite could induce unfavored non-radiative recombination, as well as inferior charge transport and extraction ^4,5.Here, we develop an impurity-healing interface engineering strategy to well address the issue both in small-area solar cell and large-scale submodule. With the introduction of a functional cation, 2-(1-cyclohexenyl)ethyl ammonium, two-dimensional (2D) perovskite with high mobility is rationally constructed on FAPbI₃ to horizontally cover the film surface and vertically penetrate to the grain boundaries of 3D perovskites. Such unique configuration not only comprehensively transforms the PbI₂ and δ-FAPbI₃ impurities into stable 2D perovskite and realize a uniform defect passivation, but also provides interconnecting channels for efficient carrier transport. As a result, the FAPbI₃-based small-area (0.085 cm²) solar cells achieve a champion efficiency over 25.86% with a notably high fill factor (FF) of 86.16%. More encouragingly, the fabricated submodules with the aperture area of 715.1 cm² obtain a certified record efficiency of 22.46% with a good FF of 81.21%, showcasing the feasibility and effectualness of the impurity-healing interface engineering for scaling-up promotion with well-preserved photovoltaic performance.