M. Nagaich, S. Campbell, and E. Aydil, “Wide band-gap CuIn1-xGaxSe2 based chalcopyrite absorbers for tandem cell application,” presented at the 37th IEEE Photovoltaic Specialists Conf., Seattle, USA, 2011.
 P. Reinhard, “Review of progress toward 20% efficiency flexible CIGS solar cells and manufacturing issues of solar modules”, IEEE Journal Of Photovoltaics, vol.3, no.1. , pp. 42-44, Jun. 2013.
 D. K. Suri, K. C. Nagpal, and G. K. Chadha, “X-ray study of CuGaxIn1-xSe2 solid solutions,” Journal of Applied Crystallography, vol. 22, no. 6, pp. 578-583, Oct. 1989.
 F. B. Dejene and V. Alberts, “Structural and optical properties of homogeneous Cu(In,Ga)Se2 thin films prepared by thermal reaction of InSe/Cu/GaSe alloys with elemental Se vapour,” Journal of Physics D: Applied Physics, vol. 38, no. 1, pp. 22, Jun. 2005.
 J. H. Scofield, A. Duda, D. Albin, B. L. Ballard,
and P. K. Predecki
, “Sputtered molybdenum bilayer back contact for copper indium diselenide-based polycrystalline thin-film solar cells,” Thin Solid Films
, vol. 260, no. 1, pp. 26-31, 1995.
 G. Gordillo, M. Grizález, and L. C. Hernandez, “Structural and electrical properties of DC sputtered molybdenum films,” Solar Energy Materials and Solar Cells, vol. 51, no. 3, pp. 327-337, 1998.
 T. Nakada and A. Kunioka, “Direct evidence of Cd diffusion into Cu(In, Ga)Se2 thin films during chemical-bath deposition process of CdS films,” Applied Physics Letters, vol. 74, no. 17, pp. 2444-2446, 1999.
 A. Kylner, “The role of the cds buffer layer in the Cu(In,Ga)Se2 thin film solar cell,” Acta Universitatis Upsaliensis, 1998.
 A. R. Jeong, R. H. Shin
, W. Jo
, M. Song
, and S. Yoon
, “Synthesis and physical properties of Cu(In,Ga)Se2 nanoparticles and CuGaSe2 thin-films for tandem cell photovoltaic applications,” presented at the 35th IEEE Photovoltaic Specialists Conf., Honolulu, USA, 2010.
 P. Reinhard, “Review of progress toward 20% efficiency flexible CIGS solar cells and manufacturing issues of solar modules,” IEEE Journal Of Photovoltaics, vol. 3, no.1, pp. 42-48, Oct 2013.
 Z. Beiley, A. Bowring, and M. D. McGehee, “Modeling low-cost hybrid tandem Photo voltaic with power conversion efficiencies exceeding 20%,” presented at the 38th IEEE Photovoltaic Specialists Conf., Austin, USA, 2012.
 A. Rohatgi, “High-throughput ion-implantation for low-cost high-efficiency silicon solar cells,” Energy Procedia, vol. 15, pp. 10-19, 2013.
 Y. G. Xiao et al., “Modeling of CdZnTe nad CIGS and tandem solar cells,” in Proc. 35th IEEE Photovoltaic Specialists Conf., Honolulu, USA, pp. 20–25, 2010.
 L. Fraas and L. Partain, Solar Cells and Their Applications, Second Edition, John Wiley & Sons, Inc., 2010.
 K. Ramanathan, M. A. Contreras, C. L. Perkins, S. Asher, F. S. Hasoon, J. Keane, D. Young, M. Romero, W. Metzger, R. Noufi, J. Ward, and A Duda, “Properties of 19.2% efficiency ZnO/CdS/CuInGaSe2 thin film solar cells, “Progress in Photovoltaics: Research and applications,” vol. 11, no. 4, pp. 225-230, 2003.
 H. Firoozi and M. Imanieh “Improvement performance CIGS thin film solar cells by changing the thickness Cd_S layer,” UCT Journal of Research in Science, Engineering and Technology, Vol5, no. 2, pp. 39-42, 2017.