Two-dimensional (2D) layered palladium dichalcogenides PdX₂ (X = S and Se) have attracted increasing interest due to their tunable electronic structure and abundant physicochemical properties. Recently, as the sister material of PdX₂, PdSSe has received increasing attention and shows great promise for technological applications and fundamental research. In the present study, we focus on the layer-dependent geometry, electronic structure, and optical properties of PdSSe using first-principles calculations. The lattice shrinkage effect present in the 2D structure is suppressed with increasing number of layers. Attributed to the strong interlayer coupling interactions, the band gap decreases from 2.30 to 0.83 eV with increased thickness. Particularly, the dispersion of the band edges on the high symmetry path changes considerably from the monolayer to bilayer PdSSe, resulting in shifts of the conduction band minimum and valence band maximum. The multilayer PdSSe shows band convergence feature with multi-valley for the conduction band, which are maintained with reduced effective mass. Furthermore, the increasing number of layers drives a wider absorption range in the visible light region, and the light absorption capability increases from ∼10% to ∼30%. Meanwhile, the band edge positions of the multilayer PdSSe are more appropriate for photocatalytic water splitting. Our theoretical study reveals the enhanced valley convergence, conductivity and optical absorption performance of the few-layer PdSSe, which suggests its promising application in thermoelectric conversion, solar harvesting and photocatalysis.

中文翻译：

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二维 PdSSe 的层依赖电子结构和光学性质

二维 (2D) 层状钯二硫化物 PdX ₂（X = S 和 Se）因其可调电子结构和丰富的物理化学性质而引起越来越多的关注。_{最近作为PdX 2}的姊妹素材, PdSSe 受到越来越多的关注，并显示出技术应用和基础研究的巨大前景。在本研究中，我们使用第一性原理计算专注于 PdSSe 的层相关几何结构、电子结构和光学特性。随着层数的增加，二维结构中存在的晶格收缩效应受到抑制。由于强烈的层间耦合相互作用，带隙随着厚度的增加从 2.30 减少到 0.83 eV。特别是，从单层到双层 PdSSe，高对称路径上带边缘的色散变化很大，导致导带最小值和价带最大值发生偏移。多层 PdSSe 显示带收敛特征，导带具有多谷，以减少的有效质量维持。此外，层数的增加驱动了可见光区域更宽的吸收范围，光吸收能力从～10%增加到～30%。同时，多层PdSSe的带边位置更适合光催化水分解。我们的理论研究揭示了少层 PdSSe 增强的谷收敛性、电导率和光吸收性能，这表明其在热电转换、太阳能收集和光催化方面具有广阔的应用前景。多层 PdSSe 的带边位置更适合光催化水分解。我们的理论研究揭示了少层 PdSSe 增强的谷收敛性、电导率和光吸收性能，这表明其在热电转换、太阳能收集和光催化方面具有广阔的应用前景。多层 PdSSe 的带边位置更适合光催化水分解。我们的理论研究揭示了少层 PdSSe 增强的谷收敛性、电导率和光吸收性能，这表明其在热电转换、太阳能收集和光催化方面具有广阔的应用前景。