As mentioned before at length, it is known that a thin layer of CdS on top of a CdTe or CIS solar cell improves their efficiency substantially. This is caused by a stationary high-field domain that is initiated adjacent to the junction interface when the bias is changed from forward to Voc to reverse bias. These domains limit the field at the junction interface below 80 kV/cm and thereby eliminate junction leakage. This causes an almost doubling of the open circuit voltage (Boer 2009a, 2010).
Fig. 37.4 High-field domain width as function of the bias for different light intensities for a Gold contact (a) and the work function of different blocking metal contacts as function of the optical generation rate a (b) (Stirn etal. 1971)