Stabilizing 1.93-eV ultrawide-bandgap perovskites for efficient triple-junction solar cells

Monolithic perovskite/perovskite/silicon triple-junction solar cells offer higher theoretical efficiency than their two-junction counterparts. However, the phase instability of ultrawide-bandgap perovskites remains a major obstacle to further improve the efficiency and stability of triple-junction devices. Here, we introduce 1,4-phenylenediamine dihydriodide into the 1.93-eV bandgap perovskite, which significantly increases the ion migration barrier and suppresses phase segregation through strong interactions with the perovskite lattice. Combined with a post-treatment using 3-(methylthio)propylamine hydroiodide to modify the perovskite surface, we achieved a certified efficiency of 26.18% for the triple-junction solar cell, with an impressive open-circuit voltage of 3.148 V on an aperture area of 1.17 cm². Notably, the encapsulated devices retained 96% of their initial performance after 1500 hours of continuous maximum power point tracking under one-sun illumination in ambient conditions, representing the notable stability in perovskite/perovskite/silicon triple-junction cells reported to date.