At present, developing new organic–inorganic hybrid materials (OIHM) and studying their photoelectric properties is an important research field. In this work, the OIHM (CH₃NH₃)₂HgCl₄ (MA₂HgCl₄) single crystal and thin film are prepared. The results show that the crystal structure of MA₂HgCl₄ has a monoclinic crystal system with P2₁/c (14) space group (unit cell dimensions 7.776 × 12.917 × 10.993 Å, 90.00 × 96.366 × 90.00) by solving the single crystal diffraction data. The band gap of MA₂HgCl₄ is calculated to be approximately 3.21 eV. To the best of our knowledge, this is the first study on MA₂HgCl₄ for optoelectronic application. The photodetector based on MA₂HgCl₄ thin film is highly selective for ultraviolet (UV) light (369 nm), and has a poor response for visible light. The electrochemical impedance spectrum shows that the impedance value (2 kΩ) of the device under 369 nm UV light is four magnitudes lower than that (10⁷ Ω) under dark. Thus, MA₂HgCl₄ has the nature of a photoconductor. The density functional theory indicates that the valence band maximum (VBM) of MA₂HgCl₄ is mainly derived from Cl‐3p state, Hg‐5d state and organic CH₃NH₃⁺ state also participate in the formation of the VBM band. The electron states of VBM and the conduction band minimum of MA₂HgCl₄ come from inorganic HgCl₄²⁻ clusters.

中文翻译：

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宽带隙有机-无机杂化（CH3NH3）2HgCl4作为自驱动紫外光电探测器和光电导体

目前，开发新型有机-无机杂化材料（OIHM）并研究其光电性能是重要的研究领域。在这项工作中，制备了OIHM（CH ₃ NH ₃）₂ HgCl ₄（MA ₂ HgCl ₄）单晶和薄膜。结果表明，通过求解单晶衍射，MA ₂ HgCl ₄的晶体结构具有P2 ₁ / c（14）空间群的单斜晶体系统（晶胞尺寸为7.776×12.917×10.993Å，90.00×96.366×90.00）数据。MA ₂ HgCl ₄的带隙计算得出大约为3.21 eV。据我们所知，这是首次将MA ₂ HgCl ₄用于光电应用的研究。基于MA ₂ HgCl ₄薄膜的光电探测器对紫外线（369 nm）具有很高的选择性，并且对可见光的响应较差。电化学阻抗谱表明，在369纳米的UV光的装置的阻抗值（2千欧）为四个幅度降低比（10 ⁷ Ω）下暗。因此，MA ₂ HgCl ₄具有光电导体的性质。密度泛函理论表明MA ₂ HgCl ₄的价带最大值（VBM）VBM带主要来自Cl-3p状态，Hg-5d状态和有机CH ₃ NH ₃ ⁺状态。VBM的电子态和MA ₂ HgCl ₄的导带最小值来自无机HgCl ₄ ^2-团簇。