A simple fabrication of high efficiency planar perovskite solar cells: controlled film growth with methylammonium iodide and green antisolvent sec-butyl alcohol

Perovskite films can be prepared using sec-butyl alcohol (2-BA) by a one-step antisolvent assisted method. However, 2-BA dissolves a necessary perovskite precursor, methylammonium iodide, CH3NH3I, (MAI), which is lost during the fabrication, leaving behind residues of another perovskite precursor, PbI2. The resulting perovskite films show reduced power conversion efficiency (PCE) and poor stability to ambient conditions. In this work, we propose an elegant strategy, i.e., the introduction of a small amount of MAI dissolved in the antisolvent 2-BA (1 mg mL−1). The additional MAI can react with the residual PbI2 during the fabrication to form the desired organic–inorganic hybrid perovskite material, CH3NH3PbI3. The high-quality of the perovskite films obtained can provide larger grain sizes and smoother surfaces, with an ideal PCE of 19.29% and superior moisture stabilities.