Effect of Al-doping on the efficiency of chemically-deposited CdS/PbS thin film solar cells

Using chemical bath deposition in an ammonia-free system, CdS/PbS solar cells have been synthesized with different Al content in their composition and varying its absorber layer thickness. Nanocrystalline CdS thin-films with an average thickness of 140 nm were prepared and, subsequently, PbS thin-films with two different thicknesses (330 and 790 nm) were grown on the CdS. X-ray diffraction studies shows that CdS and PbS thin films have a hexagonal and cubic structure, respectively. The illuminated current/ voltage characteristic curves of these p-n junctions were measured using a 300 W solar simulator at air mass 1.5, and a frequency of 50-60 Hz. It was found that Al doping decreases the conversion efficiency of the solar cells with the thinnest absorber layer, from 0.19 % to 0.05 %, and for those with thicker layers, from 0.19 % to 0.03 %.