Researchers at Nanjing University, RenShine Solar, the Zhejiang Provincial Innovation Center of Laser Intelligent Equipment Technology, Yunnan University, and Sweden's Uppsala University have developed a post-treatment technique that improves perovskite film quality on industrial textured silicon, reaching a certified tandem efficiency of 30.77%.
Schematic cross-section of the perovskite/silicon tandem cell, showing the healed perovskite layer conformally coating industrial textured silicon.
Silicon wafers textured with pyramids a few micrometers tall are an industry standard for crystalline silicon solar cells, since the texture boosts photocurrent by trapping more light and reflecting less of it away. But that same texture has held back perovskite-silicon tandem efficiencies: tandem cells built with a hybrid deposition process (evaporation followed by solution coating) on this industry-standard textured silicon have previously reached only around 31.6% certified efficiency, well below the 34.58% achieved on smoother, submicron-textured silicon that isn't used industrially. The gap traces back to perovskite film quality - the two-step process tends to produce smaller, more defective grains on the taller pyramids, and crystallization-control methods that work on flat glass generally don't transfer to the more complex textured surface.
The team's approach applies a methylammonium thiocyanate (MASCN) solution to the perovskite film after it has already formed, rather than mixing it into the original deposition solution. This "healing" step triggers secondary crystal growth through an Ostwald ripening process, producing large, conformal columnar grains that extend through the full film thickness and largely eliminate the grain boundaries that otherwise drive non-radiative recombination losses. The team traced the mechanism using in-situ SEM, XRD, and photoluminescence measurements, alongside COMSOL simulations of how the treatment solution penetrates the underlying film.
Applied to a 1.68 eV wide-bandgap perovskite top cell on a silicon heterojunction bottom cell, the treatment lifted single-junction perovskite champion efficiency to 21.1% and produced a tandem device independently certified at 30.77% (Voc of 1.915 V, Jsc of 20.13 mA/cm², FF of 79.85%) over a 1.164 cm² active area, with negligible hysteresis. A separate encapsulated tandem cell showed no measurable degradation from its initial 28.4% efficiency after 3,400 hours of continuous operation at maximum power point under one-sun illumination in ambient air - which the researchers describe as the best stability reported to date for a perovskite/silicon tandem cell.
