Inorganic Framework Composition Engineering for Scalable Fabrication of Perovskite/Silicon Tandem Solar Cells

The conformal and scalable growth of perovskite film on industrially textured silicon with a hybrid evaporation-solution method contributes to sufficient light utilization and large-scale commercialization of monolithic perovskite/silicon tandem solar cells. However, the efficacy of this approach is hindered by the incomplete reaction during the transition from spin-coating to blade-coating techniques, notably involving the buried sublimation-PbI₂. Herein, we demonstrate a triple-source coevaporation (PbI₂, PbCl₂, and CsBr) method combined with the framework-heat-treatment (FHT) strategy. Such inorganic framework composition engineering generates a quasi-two-dimensional layered structure, CsPb₂X₅, which enlarges the inorganic interlayer spacing and facilitates the penetration of organic salt solution. Consequently, a high-quality perovskite film with fully converted PbI₂ has been achieved. This advance translates into one of the best tandem solar cells that has a stabilized efficiency of 28.3% (1.05 cm²). Impressively, the encapsulated device retains 94% of its initial performance after operating for more than 1200 h under 1-sun illumination in ambient air.