Low temperature photoluminescence spectroscopy of thin film, polycrystalline CdTe/CdS solar cell structures

As-grown n-CdTe/n-CdS solar cell structures deposited on tin oxide-coated glass have been studied using low temperature photoluminescence spectroscopy. The structures were annealed in air at temperatures up to 600 degreesC. For anneal temperatures of 400-450 degreesC, and above, acceptor related transitions at around 1.45, 1.51 and 1.56 eV are tentatively ascribed to copper, oxygen and V-Cd-related centres, respectively. Illuminated current-voltage measurements have shown that these findings are consistent with considerable improvements in short circuit current density that are believed to be associated with n- to p-type conversion of the CdTe film.