Effect of Ammonium Halide Additives on the Performance of Methyl Amine Based Perovskite Solar Cells.

CH₃NH₃PbI3-xClx species were fabricated as light-absorbing layers for perovskite solar cells (PSCs), by employing NH₄I, NH₄Br, and NH₄Cl as additives via annealing at 100 °C for different times. Solutions containing CH₃NH₃I, PbI₂, and PbCl₂ (4:1:1 molar ratio) in N,N-dimethylformamide were used to prepare perovskites with NH₄I, NH₄Br, and NH₄Cl as additives, at concentrations of 0.1 M and 0.3 M. The additives helped increase the grain size and reduce pinholes in the perovskite films, as confirmed by field-emission scanning electron microscopy. The X-ray diffraction profiles of CH₃NH₃PbI3-xClx clearly showed peaks at 14° and 28° for the samples with additives, indicative of crystallinity. The best PSC performance with a power conversion efficiency of 9.13%, was achieved using 0.1 M NH₄I by annealing for 5 min, whereas the power conversion efficiency of the perovskite solar cells without additives was 5.40%.