Strained heterojunction enables high-performance, fully textured perovskite/silicon tandem solar cells

Integrating metal-halide perovskites with the industrially textured Czochralski silicon for perovskite/silicon tandem cells shows great promise for low-cost manufacturing and ideal light trapping. However, the conformal growth of high-quality perovskite film on fully textured silicon remains challenging due to the lack of effective regulation of structural evolution and residual strains. Here, we report a strain regulation strategy by forming a 3D/3D perovskite heterojunction at the buried interface through a vacuum-deposition method applicable to pyramidal texture. By tailoring the composition of buried buffer 3D perovskite, a controllable compressive strain is applied to the upper photoactive 3D perovskite, alleviating its residual tensile stress. We demonstrate that this strained heterostructure promotes the preferred crystal growth, reduces interfacial defect-induced recombination, and facilitates charge extraction. As a result, the fully textured perovskite/silicon tandem cell achieves a certified steady-state efficiency of 31.5% and retains over 95% of its initial efficiency after 800 h of continuous operation.