Prospects of thickness reduction of the CdTe layer in highly efficient CdTe solar cells towards 1 mu m

This study focuses on the technique for the stable growth of CdTe(1.44 eV) with thickness near its absorption length, 1 mu m, by close spaced sublimat ion (hereafter CSS) process, in order to achieve high conversion efficiency X-ray diffraction (XRD) spectroscopy was carried out to examine the micros tructure of the films. Current-voltage (I-V) characteristics, spectral resp onse and other features of the solar cells using these CdTe films were inve stigated to elucidate the optimum conditions for achieving the best perform ance in such thin (1 mu m) CdTe solar cells. Thickness was found to be redu ced by controlling the temperature profile used during CSS growth, The temp erature profile was found to be an important factor in growing high-quality thin films. By controlling the growth parameters and optimizing the anneal ing temperature at different fabrication steps, we have succeeded, to date, in achieving cell efficiencies of 14.3% (open-circuit voltage (V-oc): 0.82 V, short-circuit current (J(sc)): 25.2 mA/cm(2), fill factor (F.F.): 0.695 , area: 1 cm(2)) with 5 mu m, 11.4% (V-oc: 0.77 V, J(sc): 23.7 mA/cm(2),F.F .: 0.63, area: 1 cm(2)) with 1.5 mu m and 11.2% (V-oc: 0.77 V, J(sc): 23.1 mA/cm(2), F.F.: 0.63, area: 1 cm(2)) with only 1 mu m of CdTe layer thickne ss at an air mass of 1.5 without antireflection coatings. This is important for establishing a strong foundation before developing a new structure (e. g., glassn/ITO/CdS/CdTe/ZnTe/Ag configuration) with a back surface field of wide-bandgap material (e.g., ZnTe).