Butanol-assisted solvent annealing of CH3NH3PbI3 film for high-efficient perovskite solar cells

Due to the characteristics of low cost, simple process and high conversion efficiency, perovskite solar cells have become a research hotspot in recent years. In the structure of perovskite solar cell, perovskite active film plays an important role in sunlight absorption and electron–hole pair generation. This work focused on improving the quality of perovskite film by solvent annealing of perovskite film prepared with two-step spin-coating method. We chose n-butanol, a solvent with high boiling point, as an additive in CH3NH3I/isopropanol solution to execute the solvent annealing process. UV–Vis absorption spectra exhibited an enhancement in the absorbance of perovskite films with solvent annealing process. X-ray diffraction and scanning electron microscope measurements indicated that perovskite film had larger grain size after solvent annealing, especially when n-butanol content reached to 2% in the mixed solvents. The photovoltaic performance of perovskite solar cell was improved from 13.50% to the optimized 14.81%. This solvent annealing process could restrain the fast evaporation of solvent in CH3NH3I solution which is beneficial for perovskite film growth. It is found that this method has certain significance for the quality improvement of the perovskite film.