BC2P/graphene and BC2P/Black phosphorus van der Waals heterostructures with direct band gap and high carrier mobility, hardness and light absorption

In this paper, we stacked graphene, black phosphorus (BP) and a BC₂P monolayer to form one BC₂P/BP and three BC₂P/graphene (-a, -b, -c) vdW heterostructures based on examining the stability of BC₂P monolayer predicted by our group. Firstly, we discussed structures and formed possibilities of four vdW heterostructures by calculating binding energies, elastic constants and plane-averaged differential charge densities respectively, and found they are hard 2D materials even larger than the graphene. Secondly, four vdW heterostructures are direct semiconductors with the band gap as 1.053, 1.525, 0.148 and 1.085 eV under the HSE06 or PBE functional respectively, and have at least a high carrier mobility with the value as ∼10⁴ cm²/V·s or up to ∼10⁵ cm²/V·s. Thirdly, under different in-plane stresses from −6% to 6%, their optical absorption coefficient peaks shift from the ultraviolet light area to the visible light area accordingly, and the BC₂P/BP heterostructure can transfer from a metal to a semiconductor. Additionally, when the strain ratio is −6%, their absorption coefficients can reach up to the largest value respectively, especially the absorption coefficient of BC₂P/BP heterostructure can reach up to the value 29% of incident light. These results make four vdW heterostructures to be well potential materials for the application of photovoltaics and optoelectronics devices.