Photoluminescence (PL) and electroluminescence (EL) spectroscopy have been used on a series of chemically bevelled CdTe/CdS thin film solar cells to study the effects of different CdCl2 annealing times. An anneal time of 10 min was found to produce the most efficient (8.4%) cells. Evidence was found for the CdCl2 anneal promoting the formation of a CdSxTe1-x alloy near the interface. Emission at the back surface of the cells was identified as being due to the 'Y' luminescence band and a donor-acceptor pair (DAP) recombination involving cadmium vacancies and chlorine donors. Sulphur diffusion int the CdTe was estimated based on changes to the energy gap obtained from the PL data.