CIGS Device Models with Variations of Buffer Layer, Alkali Content, and Oxidation

Nine types of CIGS cells were studied with permutations of sodium content, buffer type (CdS or Zn(O, S)), and post-deposition treatment (PDT) with KF, RbF, or oxidation. JV, QE, and CV measurements are presented for several cells of each type. KF PDT with CdS buffer resulted in the highest efficiency. Although Zn(O, S) buffer cells with typical sodium content had relatively low efficiency, RbF PDT significantly improved performance. Oxidation alone significantly increased the efficiency of sodium deficient cells with CdS buffer. Numerical modeling was conducted to connect device properties to the observed performance variations.