CHARACTERIZATION OF THE ANOMALOUS 2ND JUNCTION IN MO CUINSE2 (CDZN)S ITO SOLAR-CELLS

In general any analysis of Mo/CuInSe2/(CdZn)S/ITO thin film solar cells assumes that the contacts to CuInSe2 and to (CdZn)S are ohmic. Current-voltage analysis has shown the presence of a second junction in these devices. The Mo/CuInSe2 interface was investigated as the possible location for this second junction. A scanning laser microscope with a cold stage was used to probe different regions of these devices as a function of temperature. Special devices with a transparent molybdenum back contact 400 angstrom thick were used to allow direct probing of the Mo/CuInSe2 interface through the molybdenum. The results show that a second junction exists at the Mo/CuInSe2 interface. The J-V curves for this junction as a function of temperature have been extracted from the characteristic curves of the complete device and have been accurately modeled using theory developed for quasi-ohmic contacts.