Differences of CIGS cell performance with Zn(O, S)/(Zn, Mg)O or CdS/i-ZnO buffers system explored by numerical simulations

Starting from the standard layer sequence of Mo/Cu(In, Ga)Se2/CdS/i-ZnO/ZnO:Al the cell n-side has been modified by replacing the CdS/i-ZnO with Zn(O, S) buffer in combination with (Zn, Mg)O as high-resistive layer, without changing the CIGS bulk. Measurements show a reduction of the cell performance compared to CdS/i-ZnO structure. In order to investigate the observed behavior, numerical simulations are used to examine the effect of the CIGS/Zn(O, S) interface properties on the cell performance. In particular, since the two sets of cells share the same CIGS, the effects on the solar cell's figures of merit of variations of the conduction band offset and defects properties at the buffer/absorber interface are analyzed.