Nature Energy, Published online: 10 September 2026; doi:10.1038/s41560-026-02127-1

Ultrawide-bandgap perovskites are essential for all-perovskite triple-junction solar cells, yet their high bromide content causes surface wrinkling and halide disorder, limiting the performance. A surface reconstruction and halide homogenization strategy now enables a certified efficiency of 29.3% in all-perovskite triple-junction devices.