Hybrid halide perovskites

3D halide perovskites are crystalline materials where an extended anionic network composed of corner-sharing metal-halide octahedra is charge balanced by small organic or inorganic cations. The related 2D halide perovskites can be structurally derived from 3D perovskites by slicing along certain crystallographic directions. The compositional, structural, and electronic flexibility of the 2D and 3D halide perovskites has shown great promise and enabled diverse applications including energy and optoelectronics. 

Our recent collaborative work with the Karunadasa group at Stanford on a series of 2D and 3D hybrid halide perovskites demonstrate that the pressure tuning of these materials’ structural, optical, electronic properties is of both fundamental and technological interest. By compressing a 2D Cu-Cl hybrid perovskite we showed the first instance of appreciable conductivity in such systems, and the material underwent an insulating-to-semiconducting transition (Jaffe and Lin et al., 2015). Work on 3D Pb-X (X = Br, I) hybrid perovskites demonstrated that pressure induces drastic structural, electronic, and optical modifications to the materials and could improve the performance of solar cells made of perovskites (Jaffe and Lin et al., 2016). Another study on a 2D Pb-SCN hybrid perovskite, a proposed analog to 3D Pb-I perovskite, showed a striking piezochromism from red to black to yellow from 0 to 3.8 GPa, and the material’s unusually low bandgap among 2D hybrid halide perovskites can be further modulated by very moderate pressures.