Novel Two-Dimensional MAN Materials for Photovoltaic and Spintronic Applications.

We have systematically investigated a family of newly proposed two-dimensional MAN materials (M = Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W; A = Si, Ge) using first-principles calculation. We categorize the potential of these materials into three different applications based on accurate simulation of band gap (using Hybrid HSE06 functional) and the associated descriptors. Three candidate materials (MoGeN, HfSiN, and NbSiN) turn out to be extremely promising for three different applications. MoGeN and HfSiN monolayers show strong optical absorption in the visible range, including high transition probability from the valence to conduction band. The GW+BSE calculations confirm a strong excitonic effect in both the systems. With a band gap of 1.42 eV, multilayer MoGeN shows reasonably large simulated efficiency (∼15.40%) and hence can be explored for possible photovoltaic applications. High optical absorption, suitable band gap/edge positions, and the CO activation make HfSiN monolayer a promising candidate for photocatalytic CO reduction. NbSiN, on the other hand, belongs to a new class of spintronic material called a bipolar magnetic semiconductor, recommended for spin-transport-based applications.