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. Triple-junction perovskite/perovskite/silicon solar cells promise higher efficiency, but ultrawide bandgap perovskites suffer from phase instability. Kong et al. added molecular additives and surface treatment to suppress degradation, achieving high efficiency and strong long-term stability.