A DFT Study of Optoelectronic and Photo-catalytic Properties in 2D Copper and Silver Halides Through Strain Engineering

By using first principles calculations, the electronic, optical, photo-catalytic properties and the effect of in-plane bi-axial strain are investigated for Copper halides (CuCl, CuBr, and CuI) ML and silver halides (AgCl AgBr and AgI) ML. The results show that all the studied semiconductors have indirect bandgap while under the strain of (−8% to +8%), the bandgap has changed differently. Projected density of states revealed that CBM and VBM are mainly contributed by p-orbital and d-orbital of Cu-atom respectively in the case of all Copper halides (CuCl, CuBr, and CuI). Similarly, in the case of Silver halides (AgCl, AgBr, and AgI) CBM and VBM are mainly contributed by p-orbital and d-orbital of Ag-atom respectively. Phonon band structures of all unstrained monolayers are thermodynamically stable. The computed real part ε 1 ( ω ) and the imaginary part ε 2 ( ω ) of dielectric function revealed that CuCl and CuBr are suitable for the development of devices that may work in the infrared range while other materials such as CuI, AgCl, AgBr, and AgI are suitable for the development of devices that may work in the visible range. However, all the materials have a high absorption I ( ω ) of visible light as well. I ( ω ) under the strain of (−8% to +8%) is also computed, which shows that strain can effectively increase absorption of materials in the visible region. Both E VBM and E CBM in CuCl, CuBr, CuI, AgCl, and AgBr (ML) attain favorable positions that’s why these materials are appropriate for water splitting at pH = 0 while AgI (ML) is suitable for the reduction of water but not for oxidation.