Photocapacitance analysis of defect mechanisms in Cu(In,Ga)Se2 solar cells

A photocapacitance signal is associated with trapping of carriers in the space charge region of Cu(In,Ga)Se₂ devices. The trapping centers appear to be linked to recombination centers that influence Voc. The technique is used to map out the defect structure of 5×5 arrays of devices that have intentional compositional gradients. In a controlled experiment in which the band gap is held constant while changing Ga and Se fluxes, the authors are able to observe increases in Voc that correlate directly with defects measured by photocapacitance. They have also used the technique to guide their fabrication efforts to increase the band gap of their devices without increasing the defect level