Photoluminescence study of CdTe/CdS solar cells grown from a source with Cu residual impurity

Abstract

Three photoluminescence (PL) bands centred at 1.30, 1.35 and 1.45 eV have been observed in the PL spectrum of CdTe/CdS thin film solar cells grown by close space sublimation (CSS) techniques from a source with Cu residual impurity. The bands at 1.30 and 1.45 eV were found to be independent of the technological conditions of the CSS process, while the intensity of the band at 1.35 eV proved to increase with the increase of the source temperature and the decrease of the substrate temperature. This PL band is suggested to correspond to donor-CuCd defects related to the incorporation in the CdTe film of the impurity from the source. The other two bands are associated with defects whose formation does not depend upon the technological processes applied, the band at 1.45 eV being attributed to a VCd–ClTe defect.