Cs1-xDMAxPbI3 versus CsPbI3 for Perovskite Solar Cells

Inorganic CsPbI3 perovskite solar cells (CsPbI3 PSCs) have attracted extensive attention because of their excellent thermal stability and appropriate bandgap for tandem solar cells. At present, intermediate phase engineering with organic additive, e.g., dimethyl amine iodide (DMAI), is the most common method to obtain high-efficiency CsPbI3 PSCs. However, it remains controversial whether the intermediate phase is entirely converted into a pure CsPbI3 phase. By exploring the effect of annealing temperature, herein, it is demonstrated that substantial organic residues remain in the produced films while using the current standard recipes of DMA(+)-assisted synthesis of Cs(1-x)DMA(x)PbI(3) perovskites. Thermal gravimetric and nuclear magnetic resonance show that DMA(+) remains in films annealed at a standard annealing temperature of 190 degrees C. The DMA(+) does, however, disappear if the annealing temperature is increased to 340 degrees C, which leads to a larger grain size, a contraction of the lattice, a narrower bandgap, and a redshift of the absorption onset. Though both Cs(1-x)DMA(x)PbI(3) and CsPbI3 perovskite solar cells show decent efficiencies, the pure CsPbI3 perovskite solar cells annealed at a higher temperature demonstrate higher operational stability.

Automated summary

Inorganic CsPbI3 perovskite solar cells show promise for tandem solar cells due to their excellent thermal stability and appropriate bandgap. The common method of using organic additives for intermediate phase engineering has been questioned regarding the full conversion to pure CsPbI3 phase. By studying the effect of annealing temperature, it is demonstrated that significant organic residues remain in the films when using the standard recipes of DMA(+)-assisted synthesis. However, increasing the annealing temperature to 340 degrees C eliminates the organic residues and leads to improved properties.