Halogen-halogen bonds enable improved long-term operational stability of mixed-halide perovskite photovoltaics

•Interfacial halogen-halogen bonds are introduced in 2D/3D hybrid perovskite•Interfacial suppress phase separation•Mixed halogen perovskite devices achieve long-term operational stability Perovskite-silicon tandem photovoltaics represent the most promising next-generation photovoltaic technology and could revolutionize current silicon-based technology. However, lifetimes of perovskite-silicon solar cells greatly limited by front sub-cell, which relies solely on mixed-halide perovskites. Light-induced segregation takes place perovskites due to severe ion migration, directly results device degradation and, thus, restricts stability. The issue remains challenging for whole community. We thus showcase here first time that can this separation significantly improve devices. This work opens new avenues address migration paves way development stable efficient near future. Mixed-halide provides band-gap tunability, is essential cell application. inducing seriously affects device’s represents an important challenge community urgently needs effective solutions. a strong chemical interaction, bond, at interface increasing corresponding activation energy. Various characterizations have proved form between 2D 3D phases, do halide segregation. As expected, encapsulated retains 90% initial power conversion efficiency (PCE) after maximum point (MPP) tracking ∼500 h under continuous simulated 1-sun illumination (AM 1.5) ambient conditions, representing one stable, wide-band-gap, reported so far. IntroductionHybrid-halide materials been broadly applied optoelectronic their remarkable semiconducting properties.1Lin Y.H. Sakai N. Da P. Wu J. Sansom H.C. Ramadan A.J. Mahesh S. Liu Oliver R.D.J. 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