Impact of Ga/III Profile on Voltage-dependent Collection Losses in CIGS Solar Cells

The impact of Ga/III profile changes at the front (junction) side and the back side of the device on FF and VOC loss from voltage-dependent collection was studied. Ga/III changes in the back of the device have a minimal impact on voltage-dependent collection, mostly affecting dark diode recombination. In contrast, Ga/III changes at the front side of the absorber could lead to strong FF collection losses when the Ga/III gradient creates an opposing effective force field that reduces field strength in the space-charge region. The magnitude of this loss is modulated by the defect recombination strength, as demonstrated by 1D device simulations.