High-Pressure Study of Perovskite-Like Organometal Halide: Band-Gap Narrowing and Structural Evolution of [NH₃-(CH₂)₄-NH₃]CuCl₄

Abstract

Searching for nontoxic and stable perovskite-like alternatives to lead-based halide perovskites for photovoltaic application is one urgent issue in photoelectricity science. Such exploration inevitably requires an effective method to accurately control both the crystalline and electronic structures. This work applies high pressure to narrow the band gap of perovskite-like organometal halide, [NH-(CH)-NH]CuCl (DABCuCl), through the crystalline-structure tuning. The band gap keeps decreasing below ∼12 GPa, involving the shrinkage and distortion of CuCl. Inorganic distortion determines both band-gap narrowing and phase transition between 6.4 and 10.5 GPa, and organic chains function as the spring cushion, evidenced by the structural transition at ∼0.8 GPa. The supporting function of organic chains protects DABCuCl from phase transition and amorphization, which also contributes to the sustaining band-gap narrowing. This work combines crystal structure and macroscopic property together and offers new strategies for the further design and synthesis of hybrid perovskite-like alternatives.

Synthesis, Characterization, and Optical Properties of New Organic–Inorganic Hybrid Perovskites [(NH3)2(CH2)3]CuCl4 and [(NH3)2(CH2)4]CuCl2Br2

“…The ammonium ion at the end of organic chains forms N–H···X hydrogen bonds with the halide ion of the metallic layer. The structure of inorganic layer of Cu hybrid as reported before [ 11–17 ] consists of corner‐shared octahedral distorted [CuCl 4 ] 2− anion alternative with organic layer [(NH 3 ) 2 (CH 2 ) n ] 2 cations.…”

High Compression‐Induced Conductivity in a Layered Cu–Br Perovskite

“…The chloride analog, (EA) 2 CuCl 4 , exhibits an ambient‐pressure bulk modulus ( K 0 ) of 8.4 GPa, which is ca. 10–20 GPa lower than other Cu–Cl perovskites with organic monolayers (containing diammonium molecules) or inorganic cation layers . Lower K 0 values indicate greater compressibility, decreasing the pressure necessary to induce significant structural and electronic modification.…”

Negative area compressibility of a hydrogen-bonded two-dimensional material

“…However, further compression led to the disappearance of most sharp diffraction peaks and the prominent broadening of residual peaks, which indicates that the title compound loses its crystallinity. It is well-known that hybrid organic–inorganic compounds have low resistance to hydrostatic stress and amorphization often occurs at medium pressure (usually only a few GPa) 32,33. For example, the photovoltaic hybrid perovskite (CH 3 NH 3 )PbI 3 undergoes a gradual amorphization after the structural phase transformation takes place at 2.5 GPa 34…”