Fabrication of Al-doped CIGS solar cell: The thickness-dependence of compositional, structural, optical, and photovoltaic properties

Abstract

This study presents solar cells fabricated with Al-doped CIGS employing a single-step sputtering process. The synergistic effect of Al doping and the streamlined deposition offers a simplified, scalable, and cost-effective approach, enhancing commercial viability by achieving a reduced cost-to-performance ratio. Cu (In, Ga, Al) Se₂ of various thicknesses were deposited by radio frequency RF/DC magnetron. Electron probe microanalysis (EPMA) established that Cu/(In + Ga + Al) is about 0.83 (i.e., <1, Cu-poor CIGAS). CIGAS thin films adopted a chalcopyrite phase of preferred orientation along the (112) plane, as substantiated by both X-ray diffraction. The optical band gap varied from 1.64 to 1.37 eV, when the thickness was increased from 0.2 to 2.0 μm. A series of solar cell devices of configuration SLG/Mo/CIGAS/CdS/i-ZnO/AZO/MgF₂/Ni-Al-Ni were fabricated containing a different thick absorber layer of CIGAS. The highest power conversion efficiency of 8.60 % was achieved by a 2.0 μm thick CIGAS layer deposited without post-selenization.