Baseline Models for Three Types of CIGS Cells: Effects of Buffer Layer and Na Content

Three types of CIGS cells were fabricated: 1) with CdS buffer; 2) with CdS buffer and limited sodium; and 3) with Zn(O,S) buffer. Baseline numerical models were developed with compositional grading based on GDOES data. Calculations were compared to W, QE, and CV measurements. Cells with lower sodium content exhibited higher gallium content and poor performance due to increased recombination. Similar but slightly lower efficiencies were observed for Zn(O,S) buffer cells compared CdS buffer cells. Results indicate that a highly doped p-type layer near the CIGS /buffer interface and graded defect profiles play important roles in accounting for the data.