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)2 CuBr4 (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.

中文翻译：

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层状Cu-Br钙钛矿中的高压缩诱导电导率。

我们表明，在层状卤化钙钛矿中可观的电导率的起始压力可以降低约。用Br代替Cl时的50 GPa。层状Cu-Cl钙钛矿需要大于50 GPa的压力才能显示10-4 S cm-1的电导率，而此处的Cu-Br同系物（EA）2 CuBr4（EA =乙基铵）的电导率高达2×10仅2.6 GPa时为-3 S cm-1，而在59 GPa时为0.17 S cm-1。用高能的Br 4p代替Cl 3p轨道可使钙钛矿的电荷转移带隙降低0.9 eV。在65 GPa时，该1.7 eV带隙减小至0.3 eV。高压X射线衍射，光吸收和传输测量以及密度泛函理论计算使我们能够跟踪压缩引起的结构和电子变化。Br钙钛矿的显着增强 电子对压力的响应可能归因于相对于Cl轨道更弥散的Br价轨道。这项工作将压缩诱导的钙钛矿型卤化钙的电导率提高到技术上可达到的压力。