Comparison of the compositions and structures of electrodeposited Cu-poor and Cu-rich Cu(In1-xGax)Se2 films before and after selenization

Abstract

Cu-poor and Cu-rich near stoichiometric Cu (In1-x Gax)Se2(CIGS) precursor films were obtained by one-step electrodeposition from acid aqueous baths, and the compositions and structures of the as-deposited films before and after selenization were investigated. The straightforward experimental evidence was first obtained, which showed that Cux Se compound was conglomerated as rather large crystal grains which was distributed on the surface of the film for the Cu-rich films after seleniztion. The results indicated that the film composition was changed barely after selenization. When the ratio Cu/(In+Ga)＜1.1, there were many cracks on the surface of CIGS after selenization. When Cu/(In+Ga)＞1.2, no cracks were formed on the surface of the thin films. The efficiency of solar cells bnilt directly from Cu-poor films after selenization achieved above 2%, which is pending further investigation. Furthermore, the efficiency of solar cells bult from Cu-rich CIGS films after selenization and deposition of a few In, Ga and Se by PVD has achieved 6.8%.