High-field domains in a thin cover-layer of CdS improve significantly the efficiency of CdS/CdTe solar cells

It is shown that a thin layer of CdS on top of a CdTe Solar Cell improves the efficiency by increasing mainly the open circuit voltage. This is reasoned as a result of reduced junction leakage and caused by a limitation of the maximum junction field. Such a limitation is achieved by the creation of a high-field domain in the copper-doped CdS, adjacent to the junction. The domain is initiated by field-quenching, that with further development creates a range of negative differential electron conductivity that forces the domain creation. Within the domain the field is limited to the domain field of about 80 kV/cm, that is well below initiating of any tunneling.