Surface Passivation of CIGS Solar Cells Using Gallium Oxide

This work proposes gallium oxide grown by plasma-enhanced atomic layer deposition, as a surface passivation material at the CdS buffer interface of Cu(In,Ga)Se2 (CIGS) solar cells. In preliminary experiments, a metal-insulatorsemiconductor (MIS) structure is used to compare aluminium oxide, gallium oxide, and hafnium oxide as passivation layers at the CIGS-CdS interface. The findings suggest that gallium oxide on CIGS may show a density of positive charges and qualitatively, the least interface trap density. Subsequent solar cell results with an estimated 0.5nm passivation layer show an substantial absolute improvement of 56mV in open-circuit voltage (VOC), 1mAcm2 in short-circuit current density (JSC), and 2.6% in overall efficiency as compared to a reference (with the reference showing 8.5% under AM 1.5G).