Improved phase stability of the CsPbI3 perovskite via organic cation doping.

We have studied the effect of organic cation doping with dimethylammonium (DMA+), ethylammonium (EA+), and guanidinium (GA+) on the properties of the CsPbI3 perovskite by performing first-principles calculations. It was found that these dopants, especially DMA+, can significantly improve the phase stability of the desired α phase of CsPbI3 by compressing the transition temperature between the photoactive α phase (cubic perovskite structure) and the photoinactive δ phase (orthorhombic structure). However, the incorporation of organic cations decreases the absorption coefficient of the CsPbI3 perovskite in the visible spectrum. The details of the improvement of the phase stability and the degradation of the optical properties arising from the organic dopants are revealed. Our results are valuable for developing stable and high performance hybrid perovskite photovoltaic materials.