Triple-junction solar cells with cyanate in ultrawide-bandgap perovskites

• Published in: Nature (London) Vol. 628; no. 8007; pp. 306 - 312
• Main Authors: Liu, Shunchang, Lu, Yue, Yu, Cao, Li, Jia, Luo, Ran, Guo, Renjun, Liang, Haoming, Jia, Xiangkun, Guo, Xiao, Wang, Yu-Duan, Zhou, Qilin, Wang, Xi, Yang, Shaofei, Sui, Manling, Müller-Buschbaum, Peter, Hou, Yi
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 11.04.2024; Nature Publishing Group
• Subjects: 639/301/299/946; 639/4077/909/4101/4096/946; Bromides; Crystal lattices; Crystal structure; Cyanates; Efficiency; Electron microscopy; Electrons; Energy gap; Fourier transforms; Free energy; Heat of formation; Humanities and Social Sciences; Iodides; Iodine; Maximum power tracking; Microscopy; Microstrain; multidisciplinary; Open circuit voltage; Perovskites; Photovoltaic cells; Radiative recombination; Science; Science (multidisciplinary); Silicon; Solar cells; Solar energy absorbers; Spectrum analysis; Voltage; X-ray scattering
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/s41586-024-07226-1

Perovskite bandgap tuning without quality loss makes perovskites unique among solar absorbers, offering promising avenues for tandem solar cells 1 , 2 . However, minimizing the voltage loss when their bandgap is increased to above 1.90 eV for triple-junction tandem use is challenging 3 – 5 . Here we present a previously unknown pseudohalide, cyanate (OCN − ), with a comparable effective ionic radius (1.97 Å) to bromide (1.95 Å) as a bromide substitute. Electron microscopy and X-ray scattering confirm OCN incorporation into the perovskite lattice. This contributes to notable lattice distortion, ranging from 90.5° to 96.6°, a uniform iodide–bromide distribution and consistent microstrain. Owing to these effects, OCN-based perovskite exhibits enhanced defect formation energy and substantially decreased non-radiative recombination. We achieved an inverted perovskite (1.93 eV) single-junction device with an open-circuit voltage ( V OC ) of 1.422 V, a V OC  × FF (fill factor) product exceeding 80% of the Shockley–Queisser limit and stable performance under maximum power point tracking, culminating in a 27.62% efficiency (27.10% certified efficiency) perovskite–perovskite–silicon triple-junction solar cell with 1 cm 2 aperture area. Triple-junction solar cells with cyanate in ultrawide-bandgap perovskites exhibit enhanced defect formation energy and substantially decreased non-radiative recombination.