Perovskite/Silicon Tandem Solar Cells With Stabilized Grain Boundaries

ABSTRACT Halide perovskite absorber with a bandgap near 1.68 eV is pivotal for constructing perovskite/silicon tandem solar cells. However, these wide‐bandgap perovskites are susceptible to light‐induced halide segregation and consequential non‐radiative and transport loss, severely compromising device performance and operational stability. Here, we incorporate a symmetric cross‐link agent, 4,4'‐oxydibenzenesulfonyl hydrazide, to stabilize the iodide‐bromide mixed perovskite lattice. The agents are introduced during film growth to regulate the crystallization process and subsequently assemble at grain boundaries, where they firmly anchor to the perovskite grain surface and stabilize the chemically active boundary regions. Through this approach, photostable wide‐bandgap perovskites are achieved, exhibiting enhanced crystallinity, reduced band‐tail states, and suppressed halide segregation and lattice decomposition. The resultant 1.68 eV single‐junction devices delivered an independently certified power conversion efficiency of 23.48%. When integrated with silicon heterojunction cells, the resulting two‐terminal monolithic perovskite/silicon tandem devices exhibited a power conversion efficiency of 32.19%, and retained 90% of their initial efficiency after 1020 h of continuous operation.