Computational exploration of two-dimensional silicon diarsenide and germanium arsenide for photovoltaic applications

Abstract

The properties of bulk compounds required to be suitable for photovoltaic applications, such as excellent visible light absorption, favorable exciton formation, and charge separation are equally essential for two-dimensional (2D) materials. Here, we systematically study 2D group IV–V compounds such as SiAs2 and GeAs2 with regard to their structural, electronic and optical properties using density functional theory (DFT), hybrid functional and Bethe–Salpeter equation (BSE) approaches. We find that the exfoliation of single-layer SiAs2 and GeAs2 is highly feasible and in principle could be carried out experimentally by mechanical cleavage due to the dynamic stability of the compounds, which is inferred by analyzing their vibrational normal mode. SiAs2 and GeAs2 monolayers possess a bandgap of 1.91 and 1.64 eV, respectively, which is excellent for sunlight harvesting, while the exciton binding energy is found to be 0.25 and 0.14 eV, respectively. Furthermore, band-gap tuning is also possible by application of tensile strain. Our results highlight a new family of 2D materials with great potential for solar cell applications.

Chemical and Electrochemical Lithiation of van der Waals Tetrel‐Arsenides

“…Binary GeAs and SiAs compounds, which have been known for decades, have mostly been overlooked in terms of properties until recently . These isostructural compounds are built of covalently bonded Si‐As or Ge‐As layers held together by weak van der Waals interactions.…”

“…Layered compounds have garnered increasing attention in recent years after the discovery of graphene, a single layer of graphite . Layered tetrel‐pnictides are versatile materials, displaying several interesting properties, such as superconductivity at 1.3 K in NaSn 2 As 2 and ultra‐low thermal conductivity in metallic Li 1− x Sn 2+ x As 2 .…”

“…Layered tin phosphide, Sn 4 P 3 , has been studied for lithium‐ion and sodium‐ion battery applications and has been proven to be a promising material . Pnictides of lighter tetrels such as GeAs, SiAs, GeP, SiP, GeAs 2 , and SiAs 2 have been gaining interest in the field of thermoelectrics, photovoltaics, water splitting, and optics owing to their anisotropic nature, weak interlayer interactions, relatively small band gaps (<2 eV), and potential for tuning of properties through doping and strain …”

“…Layeredc ompounds have garnered increasing attention in recent years after the discovery of graphene, as ingle layer of graphite. [1][2][3][4][5][6][7][8][9] Layered tetrel-pnictides are versatile materials, displaying severali nterestingp roperties, such as superconductivity at 1.3 Ki nN aSn 2 As 2 and ultra-low thermalc onductivity in metallicL i 1Àx Sn 2 + x As 2 . [10][11] Layered tin phosphide, Sn 4 P 3 ,h as been studied for lithium-ion ands odium-ion battery applications and has been provent ob eap romisingmaterial.…”

“…[12][13][14][15][16] Pnictides of lighter tetrels such as GeAs, SiAs, GeP,S iP,G eAs 2 , and SiAs 2 have been gaining interesti nt he field of thermoelectrics, photovoltaics, water splitting,a nd optics owing to their anisotropic nature, weak interlayer interactions, relatively small band gaps (< 2eV), and potentialf or tuning of properties through doping and strain. [4][5][6][7][8][9][17][18][19][20][21][22][23] Numerous layered ATt 3 Pn 3 (A = Na-Rb;T t= Si or Ge;P n= P or As) ternary phases have been reported in the literature; however,n one have included lithium as the alkali metalt ot he best of our knowledge. [24,25] For the larger sodium cation, a NaGe 6 As 6 structure was reported , which retains the layered structure and bondingi nb inary GeAs, but accommodates the Na atom through shifting of the layers.…”