Inorganic lead-free metal halide perovskites have garnered much attention as low-toxicity alternatives to lead halide perovskites for luminescence and photovoltaic applications. However, the electronic structure and properties of these materials, including the composition dependence of the band structure, spin–orbit coupling, and Zeeman effects, remain poorly understood. Here, we investigated vacancy-ordered Cs₃Bi₂X₉ (X= Cl, Br) perovskite nanocrystals using magnetic circular dichroism spectroscopy. Our results indicate that the excitonic spectra are predominantly composed of direct and indirect band gap transitions and that the Zeeman splitting energy of the direct exciton increases from 0.50 to 0.63 meV at 7 T by substituting Br for Cl. Comparison with analogous results for Cs₂AgBiCl₆ nanocrystals, obtained by cation substitution, suggests an important effect of charge distribution within electronic bands on the excitonic Zeeman splitting. This work demonstrates that the magneto-optical properties of these materials can be effectively manipulated via chemical composition, suggesting promising applications in photonics, spintronics, and optoelectronics.

中文翻译：

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无铅卤化物钙钛矿纳米晶体的成分可调磁光特性


无机无铅金属卤化物钙钛矿作为卤化铅钙钛矿的低毒替代品，用于发光和光伏应用，因此备受关注。然而，这些材料的电子结构和性质，包括能带结构的组成依赖性、自旋-轨道耦合和塞曼效应，仍然知之甚少。在这里，我们使用磁性圆二色谱法研究了空位排序的 Cs₃Bi₂X₉ （X= Cl， Br） 钙钛矿纳米晶体。我们的结果表明，激子光谱主要由直接和间接带隙跃迁组成，并且通过用 Br 代替 Cl，直接激子的塞曼分裂能在 7 T 时从 0.50 meV 增加到 0.63 meV。与通过阳离子取代获得的 Cs₂AgBiCl₆ 纳米晶体的类似结果进行比较，表明电子带内的电荷分布对激子塞曼分裂有重要影响。这项工作表明，这些材料的磁光特性可以通过化学成分得到有效控制，这在光子学、自旋电子学和光电子学中具有广阔的应用前景。