2-Methoxyethanol as a new solvent for processing methylammonium lead halide perovskite solar cells

Methylammonium lead halide perovskites used in photovoltaic devices are generally deposited from high boiling point solvents with low volatility such as N,N-dimethylformamide. The slow drying causes the formation of relatively large perovskite crystallites that enhance surface roughness and lead to pin holes between the crystallites. We show that the use of 2-methoxyethanol, which is a more volatile solvent, results in smaller crystals that still span the entire layer thickness. This improves the surface coverage of perovskite films, reduces the leakage current and increases the open-circuit voltage and fill factor of solar cells. P-I-N configuration solar cells, processed under ambient conditions from a triple anion (iodide, chloride, and acetate) lead precursor salt, provide an increase in the power conversion efficiency from 14.1% to 15.3% when N,N-dimethylformamide is replaced by 2-methoxyethanol as the solvent.