Lookup NU author(s): Professor Patrick Briddon
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Cu2ZnSn(S1-xSex)(4) (CZT(S, Se)) is emerging as a very credible alternative to CuIn1-xGaxSe2 (CIGS) as the absorber layer for thin film solar cells. The former compound has the important advantage of using abundant Zn and Sn instead of the expensive In and Ga. A better understanding of the properties of CZT(S, Se) is being sought through experimental and theoretical means. Thus far, however, very little is known about the fundamental properties of the CZT(S, Se) alloys. In this work, theoretical studies on the structural, elastic, electronic and optical properties of CZT(S, Se) alloys through first-principles calculations are reported. We use a density functional code (AIMPRO), along with the Pade parametrization for the local density approximation to the exchange correlation potential. For the alloying calculations we employed 64 atom supercells (approximately cubic) with a 2 x 2 x 2 k-point sampling set. These supercells possess a total of 32 chalcogen species and the CZTSe(x)S(1-x) alloys are described by using the ordered alloy approximation. Accordingly, to create a perfectly diluted alloying host, the species type of the 32 chalcogen sites is selected randomly with uniform probability x and 1 - x for Se and S, respectively. Properties of alloys (structural, elastic, electronic and optical) are obtained by averaging the results of ten supercell configurations generated for each composition. For each configuration, lattice vectors and atomic positions were allowed to relax (although enforcing the tetragonal lattice type) and the Murnaghan equation of state was fitted to the total energy data. The results presented here permit a better understanding of the properties of the CZT(S, Se) alloys which in turn result in the design of more efficient solar cells.
Author(s): Camps I, Coutinho J, Mir M, da Cunha AF, Rayson MJ, Briddon PR
Publication type: Article
Publication status: Published
Journal: Semiconductor Science and Technology
Print publication date: 26/09/2012
ISSN (print): 0268-1242
ISSN (electronic): 1361-6641
Publisher: Institute of Physics Publishing Ltd.
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