Transparent CdS films with low electrical resistivity on glass substrates were prepared by coating a CdS slurry, which contained 10 w/o $CdCl_2$, sintering in a nitrogen atmosphere at 600℃ for 2hr, and heat-treating in a nitrogen atmosphere at 600℃ for 20 min. All-polycrystalline CdS/CdTe solar cells were fabricated by coating CdTe slurries, which contained 1.0 or 4.5 w/o $CdCl_2$, on sintered CdS films and sintering from 575℃ to 700℃ for various periods of sintering. The spectral responses of sintered CdS/CdTe solar cells were measured and compared with theoretically calculated quantum efficiency. The spectral responses of teh sintered CdS/CdTe solar cells in the short-wavelength region decreases with increasing sintering time. The poor responses in this region is attributed mainly to the existence of the $CdS_yTe_{1-y}$ solid solutions in the compositional junction. The decrease in the absolute values of the spectral responses as the sintering period exceeds certain time appears to be caused by the increase in the depth of the buried homojunction and by the decrease in the acceptor densities in the P-CdTe layer. The $CdCl_2$ in the CdTe layer during sintering enchances the interdiffusion of S, Te or donor impurities across the metallurgical junction causing the formation of deeper N/P junction in the CdTe layer.
As the sintering temperature increases, the spectral responses increase due to the improvement of interfacial structures. But the absolute values of spectral response decrease as sintering exceeds certain temperature because of above described reasons.
