The article presents the development of 23.6% efficient monolithic perovskite/silicon tandem solar cells with improved stability. The researchers combined an infrared-tuned silicon heterojunction bottom cell with a cesium formamidinium lead halide perovskite top cell, which is more stable and allows for the deposition of a tin oxide buffer layer via atomic layer deposition (ALD). This buffer layer prevents shunts, has negligible parasitic absorption, and enables the sputter deposition of a transparent top electrode. The window layer also acts as a diffusion barrier, enhancing thermal and environmental stability, allowing the devices to withstand a 1000-hour damp heat test at 85 °C and 85% relative humidity. The tandem solar cells achieved a power conversion efficiency (PCE) of 23.6%, with no hysteresis and stable maximum power over more than 30 minutes under illumination. The study demonstrates the potential for achieving industry-standard operational lifetimes and raising efficiencies over 30%.The article presents the development of 23.6% efficient monolithic perovskite/silicon tandem solar cells with improved stability. The researchers combined an infrared-tuned silicon heterojunction bottom cell with a cesium formamidinium lead halide perovskite top cell, which is more stable and allows for the deposition of a tin oxide buffer layer via atomic layer deposition (ALD). This buffer layer prevents shunts, has negligible parasitic absorption, and enables the sputter deposition of a transparent top electrode. The window layer also acts as a diffusion barrier, enhancing thermal and environmental stability, allowing the devices to withstand a 1000-hour damp heat test at 85 °C and 85% relative humidity. The tandem solar cells achieved a power conversion efficiency (PCE) of 23.6%, with no hysteresis and stable maximum power over more than 30 minutes under illumination. The study demonstrates the potential for achieving industry-standard operational lifetimes and raising efficiencies over 30%.