Electronic structures and optical properties of Cu1−xNaxInSe2 by first-principle calculations

First-principle calculations on the electronic structures and magnetic properties of Na doped in CuInSe2 with different percentages reveal that the parameters and band gap increase with increasing Na. It reveals that the band gap increases 0.114 eV for 1/8 Cu replaced by Na, which exists in good agreement with the former calculation. We also discuss the differences of the complex dielectric function and the absorption spectrum of Cu1−xNaxInSe2. We find that the peak of the imaginary part of dielectric function occurs at about 1.5 eV introduces the inter-band transition of Cu-3d and Se-4p states. From the absorption spectrum, we can see that a distinct peak appears at about 2.85 eV with x=0.083x=0.083 and 0.0625 and a smooth increase without a peak appears for the other content of Na. Our result gets the right best equilibrium when x=0.0833x=0.0833 and is in good agreement with experiments.