The effect of copper on the sub-bandgap density of states of CdTe solar cells

摘要

Two optical sub-bandgap transitions in CdTe thin-film solar cells have been identified using detailed transient photocapacitance and transient photocurrent spectroscopy measurements. A broad response centered at E_V + 0.9 eV directly correlates with the quantity of Cu present in the absorber layer, while a second response at E_V + 1.2 eV does not depend on Cu or Zn and may be an intrinsic defect. These results demonstrate the influence of Cu on the sub-bandgap density of states of CdTe, and they are critical to understanding, modeling, and improving its optoelectronic properties.