Lead iodide (PbI2) has gained much interest due to its direct electronic gap in the visible range and layered crystal structure. It has thereby been considered as a promising material for applications in atomically thin optoelectronic devices. In this work, we present a detailed investigation of the effect of spin–orbit coupling (SOC) that arises from the presence of heavy atoms on the electronic and optical properties of PbI2 using first-principles calculations based on density-functional theory and many-body perturbation theory. We find that SOC not only alters the bandgap but also induces the mixing of orbital characters, resulting in a significant change in the overall band structure and charge carrier effective masses. Moreover, the band orbital mixing caused by SOC results in the dramatic change in optical transition matrix elements and, correspondingly, the absorption spectrum. Our experimentally measured absorption spectra validate the calculation results and demonstrate the importance of SOC in the optical processes of PbI2. Our findings provide insights that are important for the potential use of PbI2 as a material platform for visible optoelectronic devices.

中文翻译：

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自旋轨道对碘化铅电子和光学性质的影响

碘化铅 (PbI2) 因其在可见光范围内的直接电子能隙和层状晶体结构而备受关注。因此，它被认为是一种有前途的材料，可用于原子级薄的光电器件。在这项工作中，我们使用基于密度泛函理论的第一性原理计算，详细研究了重原子的存在引起的自旋轨道耦合 (SOC) 对 PbI2 的电子和光学性质的影响身体摄动理论。我们发现 SOC 不仅会改变带隙，还会引起轨道特征的混合，从而导致整体能带结构和载流子有效质量发生显着变化。此外，由SOC引起的带轨道混合导致光学跃迁矩阵元素的剧烈变化，并且，相应地，吸收光谱。我们通过实验测量的吸收光谱验证了计算结果，并证明了 SOC 在 PbI2 光学过程中的重要性。我们的研究结果提供了重要的见解，这些见解对于 PbI2 作为可见光电子设备的材料平台的潜在用途非常重要。