Optimization of dimethylammonium addition and effects of guanidium co-addition to CH3NH3PbI3 perovskite solar cells

The effects of adding dimethylammonium (DMA) to CH₃NH₃PbI₃ perovskite solar cells were investigated using device fabrication and first-principles calculations. For the methylammonium (MA) system, the appropriate amount of DMA to add at the MA site was found to be 30–35 %. The addition particularly contributed to the improvement of the fill factor, which enhanced the power conversion efficiencies. This was due to improved interfacial conditions, such as reduced grain boundaries resulting from increases in the crystallite size and (100) orientation. In addition, DMA and guanidinium (GA) were both added to CH₃NH₃PbI₃ perovskite solar cells, which improved the photovoltaic properties and long-term stability. This could have been due to the stabilization of the crystal structures by the co-addition of DMA/GA, which have larger ionic radii than MA. First-principles calculations suggested an increase in carrier mobility by the DMA introduction and stabilization of the crystal lattices by the co-addition of DMA/GA, which supported the effectiveness of the DMA addition.