Halide Homogenization for Low Energy Loss in 2-eV-Bandgap Perovskites and Increased Efficiency in All-Perovskite Triple-Junction Solar Cells

Monolithic all-perovskite triple-junction solar cells hold promise for surpassing the efficiency of state-of-the-art double-junction tandems and exceeding the detailed-balance limit for single junctions. However, performance remains constrained by large deficits in open-circuit voltage and underperformance in both short-circuit current density and fill factor in wide-bandgap perovskite subcells. This study identifies halide heterogeneity as a key factor in interfacial non-radiative recombination and collection efficiency losses in Br-rich perovskites. Introducing propane-1,3-diammonium iodide during fabrication improves halide homogenization, enhancing stability and achieving a record open-circuit voltage of 1.44 V.