Cs1−xDMAxPbI3versus CsPbI3for Perovskite Solar Cells

Inorganic CsPbI 3 perovskite solar cells (CsPbI 3 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 CsPbI 3 PSCs. However, it remains controversial whether the intermediate phase is entirely converted into a pure CsPbI 3 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 °C. The DMA + does, however, disappear if the annealing temperature is increased to 340 °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 CsPbI 3 perovskite solar cells show decent efficiencies, the pure CsPbI 3 perovskite solar cells annealed at a higher temperature demonstrate higher operational stability.