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

Abstract

Obtaining micron-thick perovskite films of high quality is key to realizing efficient and stable positive (p)-intrinsic (i)-negative (n) perovskite solar cells, but it remains a critical challenge. Here, we report an effective method for producing high-quality, micron-thick formamidinium-based perovskite films by forming coherent grain boundaries, where high- Miller-index-oriented grains grow on the low-Miller-index-oriented grains in a stabilized atmosphere. The resulting micron-thick perovskite films, with enhanced grain boundaries and grains, showed stable material properties and outstanding optoelectronic performances. The small-area solar cells achieved efficiencies of 26.1%. The 1-square-centimeter devices and 5 cm × 5 cm minimodules delivered efficiencies of 24.3% and 21.4%, respectively. The devices processed in a stabilized atmosphere presented a high reproducibility across all four seasons. The encapsulated devices exhibited superior long-term stability under both light and thermal stressors in ambient air.