Coherent growth of high-Miller-index facets enhances perovskite solar cells

Micron-thick perovskite films of high quality are essential for efficient and stable p-i-n perovskite solar cells, yet achieving this has been a critical challenge. This study presents a method for producing high-quality, micron-thick formamidinium-based perovskite films by creating coherent grain boundaries with high-Miller-index-oriented grains grown on low-Miller-index-oriented grains in a stabilized atmosphere. These films demonstrated enhanced grain boundaries and optoelectronic properties, achieving efficiencies of up to 26.1% in small-area cells, 24.3% in 1 cm² devices, and 21.4% in 5x5 cm minimodules. These perovskites showed high reproducibility across seasons and exceptional long-term stability under light and thermal stress.