Determination of the valence-band offset of CdS/CIS solar cell devices by target factor analysis

X-ray photoemission spectroscopy (XPS) is used to determine and compare the valence-band offsets (/spl Delta/E/sub v/) for CdS grown by chemical bath deposition on single-crystal and thin-film CuInSe/sub 2/ (CIS). The thin-film CIS device was suitable for photovoltaic energy production. By sputtering through the CdS/CIS interface and reducing the depth profile with target factor analysis, the magnitude of /spl Delta/E/sub v/ was determined to be /spl Delta/E/sub v/=1.06/spl plusmn/0.15 eV for both the single-crystal and thin-film interfaces. This determination of /spl Delta/E/sub v/ is about 0.25 eV larger than many previously reported estimations CdS grown by physical vapor deposition on CIS and helps explain the record performance of CdS/CIS photovoltaic devices.