a Division of Materials Science and Engineering, Shenzhen Graduate School, Harbin Institute of Technology, Shenzhen 518055, PR China
b Wuhan National Laboratory for Optoelectronics, College of Optoelectronic Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074, PR China
c Center for Composite Materials, Harbin Institute of Technology, Harbin 150001, PR China
Received 11 May 2011. Revised 23 July 2011. Accepted 21 November 2011. Available online 28 November 2011.
The electronic structure, dielectric function, absorption coefficient, and reflectivity of two polycrystalline semiconductors CuAlSe2 and CuAl5Se8 are studied using the density functional theory within the generalized gradient approximation. There are different peaks in the spectra of the imaginary part of the dielectric function. The transitions between the valence bands and conduction bands are discussed at length. In addition, we also notice that the reduced absorption coefficient and reflectivity near band-edge in Cu-poor CuAlSe2 are closely related to a reduction of the density of states near the valence band maximum.
