An ab initio study of the electronic structure and optical properties of CdS 1x Te x alloys Y. Al-Douri a,⇑ , Ali Hussain Reshak a,b , H. Baaziz c , Z. Charifi c , R. Khenata d,e , S. Ahmad a , U. Hashim a a Institute of Nano Electronic Engineering, University Malaysia Perlis, 01000 Kangar, Perlis, Malaysia b Institute of Physical Biology, South Bohemia University, Nove Hrady 37333, Czech Republic c Physics Department, Faculty of Science and Engineering, University of M’sila, 28000 M’sila, Algeria d Laboratoire de Physique Quantique et de Mode ´lisation Mathe ´matique (LPQ3M), Universite ´ de Mascara, 29000 Mascara, Algeria e Department of Physics and Astronomy, Faculty of Science, King Saud University, P.O. Box 2455, Riyadh 11451, Saudi Arabia Received 12 August 2010; received in revised form 6 October 2010; accepted 7 October 2010 Available online 30 October 2010 Communicated by: Associate Editor Dr. Takhir Razykov Abstract The structural, electronic and optical properties of cubic CdS 1x Te x alloys, with Te-concentrations varying from 0% up to 100% are investigated. The calculations are based on the total-energy calculations using the full potential-linearized augmented plane wave (FP- LAPW) method. The exchange and correlation potential is treated by the generalized-gradient approximation (GGA) for the total- energy calculations, while for electronic properties in addition to that the Engel–Vosko (EV-GGA) formalism was also applied. The ground state properties for all Te-concentrations are presented. The optical dielectric constant is also determined for both the binary and their related ternary alloys. Ó 2010 Elsevier Ltd. All rights reserved. Keywords: CdS 1x Te x ; EVGGA; FP-LAPW; Optical constants 1. Introduction The main feature of each solar cell is its capability to absorb effectively wide spectrum of photons contained in solar radiation reaching its active surface. This feature depends on intrinsic optical and electronic properties of semiconductor material, and the critical parameter related to semiconductor is energy band gap and energy band structure. The photons with energy lower than the absorber band gap cannot be absorbed. On the other hand one photon, even if its energy exceeds doubled value of that of the band gap, cannot generate more than single electron–hole pair, dissipating all its excess energy as a heat in the cell. The role of the absorber with these limitations in the conventional solar cell may be briefly explained as follows. For using wide band semiconductor, light absorption becomes limited only to high energy photons. The result is in lower photocurrent but the advantages are more effi- cient energy conversion of the absorbed high energy part of solar spectrum because higher fraction of photons energy is being converted into electricity, subsequently higher value of the output voltage is obtained. While solar cells made using narrow band gap semiconductors that are capable of absorbing larger part of solar spectrum and exhibit higher photocurrent values but have lower energy conversion efficiency and produce lower output voltage. Among available thin-film solar cell (a-Si, CuInGaSe 2 and CdTe) materials, cadmium telluride (CdTe) may be 0038-092X/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.solener.2010.10.006 ⇑ Corresponding author. Tel.: +60 49775021; fax: +60 49798578. E-mail address: yaldouri@yahoo.com (Y. Al-Douri). www.elsevier.com/locate/solener Available online at www.sciencedirect.com Solar Energy 84 (2010) 1979–1984