E. Salmani

SYNTHESIS AND MAGNETIC PROPERTIES OF Ni-DOPED ZnO THIN FILMS: EXPERIMENTAL AND AB INITIO STUDY

Structural and magnetic properties of Zn1−xNixO thin films and diluted magnetic semiconductors have been investigated. This sample has been synthesized using a spray pyrolysis technique with a stoechiometric mixture of zinc acetate (C4H6O4Zn⋅2H2O) and Nickel acetate (C4H6O4Ni⋅ 2H2O) on a heated glass substrate at 450∘C. The films were characterized by X-ray diffraction (XRD), UV–Vis spectrophotometry and Hall Effect measurements. These films of ZnO crystallized in the hexagonal Wurtzite structure. The optical study showed that the band-gap energy was increased, from 3.3eV to 3.5eV, with increasing the Ni concentration. The film resistivity was affected by Ni-doping, and the best resistivity value 1.15×10−2 (Ω cm) was obtained for the film doped with 2 at.% Ni. The electronic structure and optical properties of the Wurtzite structure Zn1−xNixO were obtained by first-principles calculations using the Korringa–Kohn–Rostoker method combined with the coherent potential approximation (CPA), as well as CPA confirm our results.

Band-gap engineering of CdS, CdSe and ZnSe first-principles calculations

The electronic structures of CdS, CdSe and ZnSe bulk and thin films materials are carried out Using the first principles calculations based on the Korringa-Kohn-Rostoker method (KKR) combined with the Coherent Potential Approximation (CPA). It is found that the band gaps of those materials in the case of thin films with 2, 4 and 8 layers are larger than the one of the bulk with Zinc blende structures and decreases with increasing the film thickness.

Accurate band gaps for earth-abundant photovoltaic absorber from density functional theory

First-principles calculations of the electronic and optical properties of Cu₂ZnSnSe₄ (CZTSe) and Cu₂ZnSnS₄ (CZTS) are simulated within the framework of the Korringa-Kohn-Rostoker coherent potential approximation (KKR-CPA) a sufficiently adequate approach, namely self-interaction-corrected local-density-approximation (SIC-LDA) exchange correlation potential is employed for calculating the energy band gap and electronic structure of Cu₂ZnSnSe₄ and Cu₂ZnSnS₄ based solar cells systems. This work presents detailed information about total and atom projected density of states functions, for different atoms in Cu₂ZnSnSe₄ and Cu₂ZnSnS₄. We show that density functional theory is a very powerful tool for: studying the local doping effects, defects effect, size and disorder effect on optical and electronic properties of these materials, and predicting properties of new materials.