Improvement of Cd-free CIGS solar cell efficiency using triple silicon dioxide boxes as rear-passivation

In this work, we improve Cd-free CIGS solar cell efficiency by using triple silicon dioxide (SiO₂) boxes under the CIGS layer as rear-passivation. We investigate the influence of the thicknesses, lengths, and distances of the triple SiO₂ boxes from the left and right sides of the cell. By using a thin film of SiO₂ for rear-passivation with a high density of negative charge, we observe significant improvements in cell performance. This approach effectively reduces rear-side contact recombination losses, leading to enhanced overall efficiency and performance of the solar cell. Consequently, the short circuit current density (J_sc) and fill factor experience an increase, leading to an overall enhancement in the solar cell's performance. The proposed CIGS solar cell in this paper has a fill factor of 82%. The efficiency of this solar cell is 25.8% while the last Cd-free CIGS solar cell manufactured in these dimensions has an efficiency of 23.3%. Also, by this idea, the thickness of the CIGS layer can be reduced. We have shown that with a reduction of the CIGS layer, the efficiency of the solar cell is still higher than the conventional solar cell. So the solar cell manufacturing costs will be reduced.