Deep-level impurities in CdTe/CdS thin-film solar cells

We have studied deep-level impurities in CdTe/CdS thin-film solar cells by capacitance-voltage (C-V), deep-level transient spectroscopy (DLTS), and optical DLTS (ODLTS). CdTe devices were grown by close-spaced sublimation. Using DLTS, a dominant electron trap and two hole traps were observed. These traps are designated as E1 at E-C-0.28 eV, H1 at E-V+0.34 eV, and H2 at E-V+0.45 eV. The presence of the E1 and H1 trap levels was confirmed by ODLTS. The H1 trap level is due to Cu-induced substitutional defects. The E1 trap level is believed to be a deep donor and is attributed to the doubly ionized interstitial Cu or a Cu complex. The E1 trap is an effective recombination center and is a lifetime killer. (C) 2000 American Institute of Physics. [S0021- 8979(00)02701-3].