Abstract
We systematically study, by using first-principles calculations, stabilities, electronic properties, and optical properties of GexSn1-xSe alloy made of SnSe and GeSe monolayers with different Ge concentrations x = 0.0, 0.25, 0.5, 0.75, and 1.0. Our results show that the critical solubility temperature of the alloy is around 580 K. With the increase of Ge concentration, band gap of the alloy increases nonlinearly and ranges from 0.92 to 1.13 eV at the PBE level and 1.39 to 1.59 eV at the HSE06 level. When the Ge concentration x is more than 0.5, the alloy changes into a direct bandgap semiconductor; the band gap ranges from 1.06 to 1.13 eV at the PBE level and 1.50 to 1.59 eV at the HSE06 level, which falls within the range of the optimum band gap for solar cells. Further optical calculations verify that, through alloying, the optical properties can be improved by subtle controlling the compositions. Since GexSn1-xSe alloys with different compositions have been successfully fabricated in experiments, we hope these insights will contribute to the future application in optoelectronics.
Highlights
Since the emergence of grapheme [1], two-dimensional (2D) materials have attracted intense attention in the scientific community due to richness of the physical properties [2]
These observations notably verify that through alloying GeSe and SnSe, the optical properties can be improved by subtly controlling the compositions
The structures of alloys were first generated by the tool of ATAT
Summary
Since the emergence of grapheme [1], two-dimensional (2D) materials have attracted intense attention in the scientific community due to richness of the physical properties [2]. A typical example is MoS2 [15,16,17] that has attracted tremendous attention among the TMDs materials While it has a large intrinsic band gap of 1.8 eV [18], the reported mobilities are only in the range of 0.5–3 cm V−1 s−1, which are too low for practical application in electronic devices [4]. Since experimental investigations on the composite system made by GeSe and SnSe have been successfully carried out, as far as we know, theoretical investigations related to this system have not been reported yet In this contribution, stabilities, electronic structures and optical properties of single-layer GexSn1-xSe alloys with different Ge concentrations are systematically examined on the basis of density functional calculations.
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