The optical properties and carrier mobility of MH3 (M = Co, Rh and Ir) monolayers

A new series of two-dimensional transition metal hydrides MH3 (M = Co, Rh, Ir) are investigated using first principles calculations. Their electronic structures, phonon dispersion, optical absorptions, and carrier mobilities are obtained and discussed. Our results on the basis of the Heyd–Scuseria–Ernzerhof (HSE) hybrid functional reveal that CoH3, RhH3 and IrH3 are indirect semiconductors with band gaps of 2.54 eV, 1.80 eV and 1.82 eV, respectively. Moreover, MH3 monolayers show strong optical absorption in the visible and near-ultraviolet light regions. Under tensile strain, the band gaps decrease and the optical absorption is enhanced in the visible region. The obtained carrier mobilities are found to be anisotropic along the armchair and zigzag directions. The holes along the armchair are more easily transferred with high mobility. The strong optical absorption intensity and the relatively high carrier mobilities make MH3 monolayers (especially RhH3 and IrH3) potential candidates for applications in photovoltaics.