High-Quality Concentrated Precursor Solution in N,N-Dimethylformamide for Thick Methylammonium Triiodoplumbate Layer...

A high-quality precursor solution is essential for the fabrication of hybrid perovskite solar cells. This article reports a simple and efficient method for preparing a high-quality concentrated solution of methylammonium triiodoplumbate (MAPbI₃) in N,N-dimethylformamide (DMF) by using MAPbI₃ crystals instead of conventional lead iodine and methylammonium iodine blend. The MAPbI₃ concentration of the precursor solution is easily and accurately adjusted from 0 up to 1.64 M. An investigation of the dissolution process of the MAPbI₃ crystals reveals that the concentrated solution of MAPbI₃ in DMF is metastable, and the transition from the concentrated solution to solvated intermediate MAPbI₃·DMF determines the solubility of MAPbI₃ in DMF. The high purity and precise stoichiometric ratio of the crystals eliminate the possible impurities that initialize the transition to MAPbI₃·DMF and consequently suppress the transition and increase the stability of the concentrated solution. MAPbI₃ films with different thicknesses up to 800 nm are prepared with the conventional film fabrication technique, and the highest power conversion efficiency of 20.7% is achieved on corresponding solar cells. This newly developed method for preparing a concentrated precursor solution can be easily combined with other fabrication techniques for further development of industrial-scale manufacture of solar cells.