The effect of defects on Cu-doped CdS: A first-principles study Yuxiang Liu, Jie Lian, Minglin Zhao, Ying Wang, Mengmeng Li and Haonan Song EPL, 117 5 (2017) 57007 Published online: 09 May 2017 DOI: 10.1209/0295-5075/117/57007