Preserving a robust CsPbI3 perovskite phase via pressure-directed octahedral tilt

Functional CsPbI3 perovskite phases are not stable at ambient conditions and spontaneously convert to a non-perovskite delta phase, limiting their applications as solar cell materials. We demonstrate the preservation of a black CsPbI3 perovskite structure to room temperature by subjecting the delta phase to pressures of 0.1 - 0.6GPa followed by heating and rapid cooling. Synchrotron X-ray diffraction and Raman spectroscopy indicate that this perovskite phase is consistent with orthorhombic gamma -CsPbI3. Once formed, gamma -CsPbI3 could be then retained after releasing pressure to ambient conditions and shows substantial stability at 35% relative humidity. First-principles density functional theory calculations indicate that compression directs the out-of-phase and in-phase tilt between the [PbI6](4-) octahedra which in turn tune the energy difference between delta- and gamma -CsPbI3, leading to the preservation of gamma -CsPbI3. Here, we present a high-pressure strategy for manipulating the (meta)stability of halide perovskites for the synthesis of desirable phases with enhanced materials functionality. Inorganic lead halide perovskites are structurally unstable, which prevents their application in solar cells. Here the authors synthesize, using high pressure and temperature, a perovskite CsPbI3 phase that is metastably preserved to ambient conditions through a structural deformation induced at high pressure.

Automated summary

By manipulating the stability of inorganic lead halide perovskites through high pressure treatment and structural deformation induced at high pressure, the authors have synthesized a CsPbI3 perovskite phase that is preserved at ambient conditions, potentially enhancing material functionality.