Abstract In the current study, we explore theoretically electronic and optical properties of penta-SiC2 and -SiGeC4 monolayers based on ab initio computations and utilizing modified Becke–Johnson generalized gradient-approximation (mBJ-GGA) within the density functional theory. The calculated results show that both 2D penta-SiC2 and -SiGeC4 are structurally stable, according to their negative formation energy. Furthermore, we have found that the penta-SiC2 and -SiGeC4 semiconductors show indirect and moderate band gaps of 1.75 and 1.62 eV by employing mBJ-GGA functional, respectively. Also, these systems present sigma- and pi-bond between two nearest neighbor carbon atoms by overlapping sp2-sp2 and p-p orbitals, respectively, as well as an ionic bond between two nearest neighbor Si-C and Ge-C atoms. Additionally, we have shown that the considered compounds exhibit small reflectivity and high absorption peaks in visible region with the shift of absorption edge of 2D penta-SiGeC4 to the low energy visible region due to its small band gap compared to that of 2D penta-SiC2. These findings make both penta-SiC2 and -SiGeC4 monolayer semiconductors promising candidates for photovoltaic technology.

中文翻译：

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五-SiC2和-SiGeC4单层的电子和光学特性

摘要 在当前的研究中，我们基于从头计算并利用密度泛函理论中的修正贝克-约翰逊广义梯度近似 (mBJ-GGA) 从理论上探索了五-SiC2 和-SiGeC4 单层的电子和光学特性。计算结果表明，根据它们的负形成能，2D penta-SiC2 和-SiGeC4 在结构上都是稳定的。此外，我们已经发现，通过使用 mBJ-GGA 功能，penta-SiC2 和 -SiGeC4 半导体分别显示出 1.75 和 1.62 eV 的间接和中等带隙。此外，这些系统分别通过重叠 sp2-sp2 和 pp 轨道，以及两个最近的相邻 Si-C 和 Ge-C 原子之间的离子键，在两个最近的相邻碳原子之间呈现 sigma 和 pi 键。此外，我们已经表明，所考虑的化合物在可见光区表现出小的反射率和高吸收峰，由于与 2D penta-SiC2 相比，其带隙较小，因此 2D penta-SiGeC4 的吸收边缘向低能量可见光区移动。这些发现使五-SiC2 和-SiGeC4 单层半导体成为光伏技术的有希望的候选者。