Precursor reaction method with high Ga Cu(In,Ga)(S,Se)2 to achieve increased open-circuit voltage

The precursor reaction method for the fabrication of Cu(In,Ga)Se
₂
(CIGS) solar cells potentially allows for low-cost fabrication and scalable processing for manufacturing. Additionally, this process has yielded record efficiencies in lab scale experiments. Thus far, research on the precursor reaction method has been restricted to relatively low Ga compositions in CIGS (Ga/(In+Ga) ≈ 25%). By increasing the ratio of Ga, it is possible to increase bandgap and thus increase open circuit voltage. This work focuses on developing and characterizing the precursor reaction process for use with the higher Ga regime, with the goal of improving open circuit voltage and efficiency. It is shown that with increased Ga ratio, the rate of conversion from precursor to absorber phases is decreased. Additionally, increased Ga improves film adhesion at increased selenization temperatures as well as improving film morphology.