Solvent engineering for forming stonehenge-like PbI2 nano-structures towards efficient perovskite solar cells

Abstract

The organic–inorganic lead halide layer is a crucial factor in determining the photovoltaic performance of perovskite solar cells. Based on solvent engineering, we developed a three-step sequential coating method to prepare a high-quality CH₃NH₃PbI₃ layer based on solvent (isopropanol) substitution. Stonehenge-like PbI₂ nanostructures with controllable morphology and crystallinity were prepared by solvent substitution instead of the conventional annealing-treatment, affording several channels for CH₃NH₃I to penetrate into the PbI₂ film due to volume expansion, and thus enabling the complete conversion from PbI₂ to perovskite. In addition, the device exhibited high reproducibility by our method and achieved a high 17.78% power conversion efficiency under one-sun illumination. Furthermore, we optimized the production craft and successfully fabricated a uniform perovskite film (10 cm × 10 cm) via solvent substitution.