Mixed-halide perovskite provides band-gap tunability, which is essential for tandem solar cell application. However, ion migration inducing phase segregation seriously affects the device’s long-term operational stability. The issue thus represents an important challenge for the whole perovskite community and urgently needs effective solutions. We showcase here for the first time that a strong chemical interaction, a halogen-halogen bond, is introduced at the phase interface to suppress the ion migration by increasing the corresponding activation energy. Various characterizations have proved that halogen-halogen bonds form between 2D and 3D phases, which do suppress the halide segregation. As expected, the encapsulated device retains 90% of initial power conversion efficiency (PCE) after maximum power point (MPP) tracking for ∼500 h under continuous simulated 1-sun illumination (AM 1.5) in ambient conditions, representing one of the most stable, wide-band-gap, mixed-halide perovskite photovoltaics reported so far.

混合卤化物钙钛矿提供带隙可调性，这对于串联太阳能电池应用至关重要。然而，离子迁移引起的相分离严重影响了器件的长期运行稳定性。因此，该问题代表了整个钙钛矿社区的重要挑战，迫切需要有效的解决方案。我们在这里首次展示了在相界面引入了强化学相互作用，即卤素 - 卤素键，通过增加相应的活化能来抑制离子迁移。各种表征已经证明在 2D 和 3D 相之间形成卤素 - 卤素键，这确实抑制了卤化物偏析。正如预期的那样，