MICROSTRUCTURAL CHARACTERIZATION FOR SPUTTER-DEPOSITED CUINSE2 FILMS AND PHOTOVOLTAIC DEVICES

Comparative study on the microstructural and photoluminescence (PL) properties of CuInSe2 films deposited by both three-source sputtering and hybrid sputtering was carried out by high-resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), PL spectroscopy and X-ray diffraction analysis. The CuInSe2 films deposited by three-source sputtering exhibited small grain size and considerably high density of lattice defects, which led to poor cell performance. In contrast, hybrid-sputtered films showed relatively large grain size and low density of defects. Significant difference in PL spectra was also observed between CuInSe2 films deposited by both methods. ZnO:Al/CdS/CuInSe2 solar cell with an active-area efficiency of 11.3% was achieved using hybrid-sputtered material. The correlation between microstructural properties and device performance suggests that the decreasing defect density in CuInSe2 films is essential for achieving high efficiency solar cells by sputtering process.