Longitudinal Homogenized Intermediates Facilitate Air-Processed Hybrid Sequential Deposition of Perovskite/Silicon Tandem Solar Cells

Hybrid sequential deposition (HSD) of perovskite thin films is highly desirable for constructing tandem solar cells on textured silicon substrates. However, in the second step of HSD, where the inorganic and organic bilayers undergo thermal interdiffusion to form perovskite, performance is often limited by the need for a very dry environment (inert gas atmosphere or dry air with relative humidity below 10%) and incomplete reactions throughout the film thickness. Here, we demonstrate a longitudinal homogenized intermediate (LHI) strategy that enables the preparation of HSD perovskites under ambient conditions (25 °C, 30%–50% relative humidity). This approach circumvents the formation of a perovskite capping layer, promoting uniform interdiffusion of the organic–inorganic bilayer. As a result, the efficiency of 1.68 eV perovskite solar cells processed in air using HSD improved from 16.42% to 20.65%, leading to an efficiency of 28.55% for textured perovskite/silicon tandem cells.