DOI: 10.11648/j.eas.20261105.12 ISSN: 2575-1468

Effect of CIGS Absorber Thickness on the Performance of In 2 S 3 -Buffered Thin-Film Solar Cells: Role of the MgF 2

Papa Sow, Cheick Goudiaby, Alioune Ngom, Jacques Faye, Ahmed Mohamed-Yahya, Mamadou Samb
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This work numerically investigates, using the Silvaco ATLAS simulator, a thin-film solar cell based on a Cu(In,Ga)Se₂ (CIGS) absorber combined with a non-toxic In 2 S 3 buffer layer replacing conventional CdS, building on an earlier doping-optimization study that identified N A = 3×10 16 cm -3 as optimal for both configurations investigated (with and without a MgF 2 antireflection coating). At this doping level, two otherwise identical structures, one with MgF 2 and one without, are compared to isolate the effect of CIGS absorber thickness (0.5 to 4 µm) on J sc , V oc , FF and η. Efficiency increases monotonically with thickness, reaching 24.7% with MgF 2 and 21.93% without at 4 µm, a nearly constant relative gain of about 12.6% attributable almost entirely to the increase in short-circuit current. The analysis also tracks the effective series (R s ) and shunt (R sh ) resistances extracted from the simulated J–V curves to clarify the mechanism behind the improvement of the fill factor with thickness. The decrease in Rs and increase in R sh are consistent with reduced electrical losses in thicker absorbers, though these values are read as effective electrical descriptors rather than direct proof of a microstructural change, since no grain-boundary or defect-density model was varied with thickness. A marginal-gain analysis of the full thickness interval, combined with a relative active-material-use analysis, identifies 2–3 µm with MgF 2 as the best trade-off between performance and material use. A particularly compact illustration is that a 1 µm CIGS cell with MgF 2 (η = 22.17%) already outperforms a 4 µm cell without MgF 2 (η = 21.93%), using only a quarter of the absorber volume, showing that improved front-surface optical management can compensate for a substantial reduction in absorber thickness.

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