Hybrid inorganic-organic perovskites attracted increasing attention because of variety of their applications in the fields of photovoltaics, photoelectronics and switchable dielectric devices. Diverse molecular functional materials can be assembled by modifying the length of the organic components and inorganic framework dimensionality and, thus, they might be promising candidates to obtain phase-transition materials. In this study, we present a new hybrid perovskite-like compound, (ClC₂H₄NH₃)₂CuBr₄ (I), which follows the two-dimensional inorganic frameworks of the corner-sharing CuBr₆ octahedra. Strikingly, compound (I) displays a dielectric phase transition at around 275 K, changing from the non-centrosymmetric space group of Pc (LT phase) to centrosymmetric P2₁/a (HT phase) upon heating. The crystal structure analyses reveal that the unusual thermally activated conformation change of the 2-chloroethylammonium cations and distortions of CuBr₆⁴⁻ network in the inorganic layers afford the driving force to the phase transition. Moreover, the Jahn−Teller distortion introduces elongation of coordination bonds in the inorganic planes, which confers higher flexibility to the structure. Compound (I) displays phase transitions at T₁ = 270 K and T₂ = 323 K, confirmed by DSC measurements. In addition, the UV/Vis optical spectrum indicates that (I) has an indirect band gap of 1.47 eV. This finding may extend the application of 2D layered lead-free hybrid perovskite-type materials to the field of photovoltaic as the photo absorber layer of solar cells.

杂化无机-有机钙钛矿因其在光伏，光电和可切换介电器件领域的各种应用而引起了越来越多的关注。可以通过改变有机成分的长度和无机骨架的尺寸来组装各种分子功能材料，因此，它们可能是获得相变材料的有希望的候选者。在这项研究中，我们提出了一种新的杂化钙钛矿样化合物，（ClC ₂ H ₄ NH ₃）₂ CuBr ₄（I），该化合物遵循角共享CuBr ₆八面体的二维无机骨架。令人惊讶的是，化合物（I）在275 K附近显示出介电相变，加热时从非中心对称的Pc组（LT相）变为中心对称的P 2 ₁ / a（HT相）。晶体结构分析表明，无机层中2-氯乙基铵阳离子的异常热活化构象变化和CuBr ₆ ^4-网络的变形为相变提供了驱动力。此外，Jahn-Teller变形在无机平面中引入了配位键的延伸，从而赋予了结构更高的灵活性。化合物（I）在T ₁  = 270 K和T _2时显示相变 = 323 K，由DSC测量确认。另外，UV / Vis光谱表明（I）具有1.47eV的间接带隙。该发现可以将2D层状无铅混合钙钛矿型材料的应用扩展到作为太阳能电池的光吸收层的光伏领域。