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All-inorganic CsPbI3perovskite has a near-ideal band gap, high thermal stability, and simple material composition, thus presenting a promising option for developing perovskite/Si tandem solar cells. However, CsPbI3undergoes a rapid phase transition under exposure to moisture and exhibits a significant performance gap relative to other perovskite compounds, particularly in the p-i-n structure favored for perovskite/Si tandems. Here, we demonstrate highly efficient and stable p-i-n-structured CsPbI3perovskite solar cells by surface engineering the CsPbI3layer with oxidized Ti3C2TxMXene (OMXene) nanoplates via spray coatings. OMXene provides a physical barrier against moisture and improves charge separation at the perovskite-electron transporting layer interface via an enhanced electric field. Consequently, we demonstrated CsPbI3/OMXene-based p-i-n devices with efficiencies of 19.69% for 0.096-cm2cells and 14.64% for 25-cm2minimodules. The encapsulated minimodule showed good stability, retaining ∼85% of the initial efficiency under simultaneous damp heat (85°C/85% relative humidity) and 1-sun light soaking for over 1,000 h.

Inorganic perovskite solar cells (PSCs) are promising for achieving long-term operational stability with good device performance. Here, we report the fabrication of inorganic CsPbI2Br-based perovskite thin films with a well-defined CsPbI3−xBrxcomposition gradient in the surface region by a scalable, orthogonal processable spray-coating approach. The graded structure broadens absorption wavelength range and increases carrier lifetime, but it also causes electrical field redistribution within a device stack for more efficient charge separation and collection. With this approach, we obtained a power conversion efficiency of 16.81% for a 0.096-cm2PSC. We further demonstrated a monolithically integrated perovskite submodule based on the graded CsPbI3−xBrxby spray coating with an efficiency of 13.82% (112-cm2aperture area) and ∼9% degradation over 1,000-h continuous 1-sun light soaking.