The Pb-free hybrid-layered-double perovskites (HLDPs) have been proposed as green and stable semiconducting materials for optoelectronic devices, but the synthesized members are still limited. Here, we report the synthesis of three new HLDPs, (C₈H₂₀N₂)₂AgMBr₈ (M = In, Sb, and Bi), by a solution method using 1,4-bis(ammoniomethyl)cyclohexane (C₈H₂₀N₂²⁺) as the organic spacing cation. All three of these HLDPs show ⟨100⟩-oriented layered structures with Ag and In/Sb/Bi order arranged in corner-sharing octahedral layers. The first-principle calculations indicate the indirect-gap nature of (C₈H₂₀N₂)₂AgInBr₈ and (C₈H₂₀N₂)₂AgSbBr₈, while their Bi counterpart shows a direct band gap after considering spin–orbit coupling. The band gaps obtained by diffuse-reflectance spectroscopy are 3.11, 2.60, and 2.70 eV for M = In, Sb, and Bi, respectively. (C₈H₂₀N₂)₂AgInBr₈ shows a broadband red emission centered at 690 nm, and it is mainly attributed to the self-trapped-excitons mechanism. Our results not only provide a series of new “Pb-free” HLDPs with chemical diversity but also help us to further understand the structure–property relationships of HLDP materials.

中文翻译：

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混合层状双钙钛矿 (C8H20N2)2AgMBr8（M = In、Sb 和 Bi）的结构和光学特性

无铅混合层状双钙钛矿（HLDPs）已被提议作为用于光电器件的绿色且稳定的半导体材料，但合成的成员仍然有限。在这里，我们报告了三种新的 HLDP，(C ₈ H ₂₀ N ₂ ) ₂ AgMBr ₈ (M = In、Sb 和 Bi)，通过使用 1,4-双（氨甲基）环己烷（C ₈ H ₂₀ N ₂ ²⁺ ) 作为有机间隔阳离子。所有这三个 HLDP 都显示出 ⟨100⟩ 取向的层状结构，其中 Ag 和 In/Sb/Bi 顺序排列在共享角的八面体层中。第一性原理计算表明 (C ₈ H₂₀ N ₂ ) ₂ AgInBr ₈和(C ₈ H ₂₀ N ₂ ) ₂ AgSbBr ₈，而他们的Bi对应物在考虑自旋轨道耦合后显示出直接带隙。对于 M = In、Sb 和 Bi，通过漫反射光谱获得的带隙分别为 3.11、2.60 和 2.70 eV。(C ₈ H ₂₀ N ₂ ) ₂ AgInBr ₈显示以 690 nm 为中心的宽带红色发射，这主要归因于自陷激子机制。我们的研究结果不仅提供了一系列具有化学多样性的新型“无铅”HLDP，而且有助于我们进一步了解 HLDP 材料的结构-性能关系。