Solvent engineering for forming stonehenge-like PbI2 nano-structures towards efficient perovskite solar cellsElectronic supplementary information (ESI) available. See DOI: 10.1039/c6ta11004e

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 CH 3 NH 3 PbI 3 layer based on solvent (isopropanol) substitution. Stonehenge-like PbI 2 nanostructures with controllable morphology and crystallinity were prepared by solvent substitution instead of the conventional annealing-treatment, affording several channels for CH 3 NH 3 I to penetrate into the PbI 2 film due to volume expansion, and thus enabling the complete conversion from PbI 2 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. Stonehenge-like PbI 2 nanostructure, prepared via solvent substitution, provides important progress for scalable fabrication and highly efficient perovskite solar cells.