CuInS ₂ quantum dots for the performance enhancement in commercial Si solar cells

Abstract Silicon-based solar cells dominate the photovoltaic market but face efficiency limits from incomplete use of the solar spectrum. This study explores CuInS 2 quantum-dot (QD) thin films, applied by spin-coating as spectral conversion layers to boost device performance. We systematically investigated how spin speed, varied between 2000 and 6000 rpm, determines film thickness (78 −54 nm) and power conversion efficiency. QD-only coatings delivered efficiency gains ranging from 0.9%–2.2%, while PMMA–QD composite films produced 1.1%–3.7% improvements, with the most consistent results observed for thinner films produced at higher spin speeds. The CuInS 2 QDs displayed strong ultraviolet absorption, while their broad visible photoluminescence centered near 660 nm aligns with the silicon spectral response. Incorporating QDs into a PMMA matrix enhanced coating reproducibility while preserving efficiency benefits, confirming the QDs as the primary source of performance gains. These findings demonstrate that spin-coated CuInS 2 QD layers, either standalone or embedded in a polymer matrix, offer a scalable, eco-friendly strategy for improving commercial silicon solar cell efficiency.