Solvent washing with toluene enhances efficiency and increases reproducibility in perovskite solar cells

We report a simple process for reproducibly fabricating perovskite solar cells. We emphasize that the solvent washing technique is the most practical method for successful uniform crystallization so it facilitates highly efficient reproducible perovskite solar cells. The critical parameter for tuning crystallinity is determined to be the type of washing solvent and the quantity dispensed. The amount of washing solvent strongly affects the particle size distribution resulting in better or worse interconnection between the crystal grains. We discovered that 20 mu l of toluene is the best washing solvent for device reproducibility. Our proposed parameters result in 90% reproducible perovskite solar cells with an average efficiency around 8%.