Computational Dissection of 2D SiC7 Monolayer: A Direct Band Gap Semiconductor and High Power Conversion Efficiency

Abstract

AbstractIt is well known that zero‐gap character of graphene and silicene limits their applications, which stimulates the great passions to open an energy gap in graphene (silicene) and develop their application in optoelectronic devices. Recently, it is reported that SixC1 − x monolayers hold great potential in solar cells. In this paper, based on the global particle‐swarm optimization algorithm and the density functional theory methods, two new novel stable SiC7 (α‐SiC7 and β‐SiC7) was predicted, which are 22 meV per atom and 86 meV per atom lower than g‐SiC7 in energy, respectively. Among them, β‐SiC7 presents graphene‐like honeycomb configuration, having a direct band gap of 1.01 eV, which covers the main energy of the solar spectrum. Moreover, its hole mobility can reach ≈10 000 cm2 V−1 s−1, which is much higher than that of silicon. These advantages make it a promising candidate as a donor material for excitonic solar cells. The authors’ theoretical simulations show a considerably high power conversion efficiency of 20.5% for the primarily designed β‐SiC7/g‐SiC7 excitonic solar cells.