Efficiency Enhancement of CIGS Solar Cells with BSF Layer and Graded-Bandgap Absorber Layer

The efficiency of conventional copper indium gallium selenide (CIGS) solar cells is lower than that of silicon-based solar cells. The use of expensive materials such as indium and gallium raise the manufacturing cost. The efficiency of conventional CIGS solar cells is compared in this study by using Tin (II) sulfide (SnS) as an economical back surface field layer (BSF) and a graded bandgap absorber (CIGS) layer. In this investigation, a conventional CIGS structure comprising of Al/ZnO/CdS/CIGS/Mo was used as a reference. During the initial stage, A BSF layer was introduced to the conventional structure. It had a 28.18% efficiency using a thickness of 0.8
$\mu \mathrm{m}$
CIGS layer and thickness of 0.3
$\mu \mathrm{m}$
ultrathin SnS layer. The conventional structure was treated with a 1.1
$\mu \mathrm{m}$
thick graded bandgap CIGS layer in the second stage. A structure known as a graded CIGS layer is one in which the bandgap of the material varies depending on the concentration of gallium present. The bandgap in this investigation ranged from 0.10 to 0.35 eV, yielding in a cell efficiency of 23.55%. These findings bode well for more efficient and cost-effective solar cell production.