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

Abstract

We show that the onset pressure for appreciable conductivity in layered copper‐halide perovskites can decrease by ca. 50 GPa upon replacement of Cl with Br. Layered Cu–Cl perovskites require pressures >50 GPa to show a conductivity of 10−4 S cm−1, whereas here a Cu–Br congener, (EA)2CuBr4 (EA=ethylammonium), exhibits conductivity as high as 2×10−3 S cm−1 at only 2.6 GPa, and 0.17 S cm−1 at 59 GPa. Substitution of higher‐energy Br 4p for Cl 3p orbitals lowers the charge‐transfer band gap of the perovskite by 0.9 eV. This 1.7 eV band gap decreases to 0.3 eV at 65 GPa. High‐pressure X‐ray diffraction, optical absorption, and transport measurements, and density functional theory calculations allow us to track compression‐induced structural and electronic changes. The notable enhancement of the Br perovskite's electronic response to pressure may be attributed to more diffuse Br valence orbitals relative to Cl orbitals. This work brings the compression‐induced conductivity of Cu‐halide perovskites to more technologically accessible pressures.

Hybrid Layered Double Perovskite Halides of Transition Metals

“…[9][10][11] There has separately been considerable progress in the development of layered single perovskite halides of 2+ transition metals (TMs). [12][13][14][15][16] In addition, there is a report of mixed-valence Au + /Au 3+ based perovskite iodides containing [Au I Au III I6] 2layers of linear [Au I I2]and square planar [Au III I4]ions. 17 However, the family of typical HLDP halides has not yet been extended to heterometallic and magnetic systems with 1+ and 3+ TMs.…”

Ferroelectric Modulation in Flexible Lead‐Free Perovskite Schottky Direct‐Current Nanogenerator for Capsule‐Like Magnetic Suspension Sensor

“…The UV–vis–NIR spectroscopy displays two distinct absorption peaks at ≈265 and 370 nm, and one broad peak from 650 to 850 nm, which are assigned to the π ‐to‐ π * transition of DF‐CBA + , ligand‐to‐metal charge transfer and Cu 2+ d ‐ d transitions, respectively (Figure 2b). [ 67,68 ] From the cut‐off curve of the Tauc plot result, the band gap of (DF‐CBA) 2 CuCl 4 thin film is ≈2.43 eV, which is larger than the ideal band gap range (1.48–1.62 eV) for perovskite‐based photovoltaic devices. [ 69 ] To confirm the Schottky contact between the Al and perovskite, a PEDOT: PSS‐coated glass/(DF‐CBA) 2 CuCl 4 /Al device was prepared for the current–voltage ( I ‐ V ) measurements.…”

Quasi-One-Dimensional Metallicity in Compressed CsSnI3

“…Lattice compression has been used to effectively modify the electronic structures and improve the conductivity of halide perovskites. − Low-dimensional metal halides indeed attracted extensive attention in the high-pressure community in the past years. − These studies centered on tuning the materials’ structural, electronic, and optical properties. So far, the electronic anisotropy in these materials has not been used to realize intriguing electronic states, e.g., 1D metallicity.…”