Impurity-healing interface engineering for efficient perovskite submodules

An issue that affects the scaling-up development of perovskite photovoltaics is the marked efficiency drop when enlarging the device area, 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 unfavoured non-radiative recombination, as well as inferior charge transport and extraction^4,5. Here we develop an impurity-healing interface engineering strategy to address the issue in small-area solar cells and large-scale submodules. With the introduction of a functional cation, 2-(1-cyclohexenyl)ethyl ammonium, two-dimensional perovskite with high mobility is rationally constructed on FAPbI₃ to horizontally cover the film surface and to vertically penetrate the grain boundaries of three-dimensional perovskites. This unique configuration not only comprehensively transforms the PbI₂ and δ-FAPbI₃ impurities into stable two-dimensional perovskite and realizes 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 of more than 25.86% with a notably high fill factor of 86.16%. The fabricated submodules with an aperture area of 715.1 cm² obtain a certified record efficiency of 22.46% with a good fill factor of 81.21%, showcasing the feasibility and effectualness of the impurity-healing interface engineering for scaling-up promotion with well-preserved photovoltaic performance.