Researchers at Xiamen University, Jinan University, Tsinghua University, Xi'an Jiaotong University, Uppsala University in Sweden, the Institute of High Energy Physics of the Chinese Academy of Sciences, the Shanghai Advanced Research Institute of the Chinese Academy of Sciences, and Guangdong Mellow Energy have developed a Prussian blue-based strategy to control both crystallization and ion migration in perovskite solar cells, achieving a champion efficiency of 26.9% in small-area cells that held up at scale in large submodules.
The team incorporated a lattice-matched Prussian blue scaffold into the perovskite film as a structural template. Using in situ grazing-incidence wide-angle X-ray scattering (GIWAXS) and X-ray absorption fine structure (XAFS) measurements at the Beijing and Shanghai Synchrotron Radiation Facilities, they found that the Prussian blue framework converts the film's typically uncontrolled, homogeneous nucleation into a more ordered, heterogeneous process. It suppressed the formation of non-photoactive δ-FAPbI₃ phases in favor of the photoactive α-FAPbI₃ phase, promoted crystal growth along a preferred orientation, and relieved tensile strain in the film. Separately, the framework's redox-active Fe–C≡N–Fe network helped convert lead⁰ and iodine⁰ defects, while its rigid, open cage structure locked mobile cations in place, suppressing the ion migration that normally degrades perovskite devices under operation.
The strategy yielded champion power conversion efficiencies of 26.1% in n-i-p architecture and 26.9% in p-i-n architecture (26.2% certified) for small-area cells. Scaling up, the team reached 23.4% in 6×6 cm minimodules and a certified 22.9% in 30×30 cm submodules. Submodules with initial efficiencies of 20.2–21.0% showed no discernible decline relative to a silicon reference cell over five months of outdoor testing, alongside robust performance under accelerated aging.
