Vertical deposition method of gold nanorods at the anodic interface for enhanced organic solar cell performance

In this study, we presented a straightforward and cost-effective strategy to enhance the photovoltaic performance of poly(3-hexylthiophene-2,5-diyl):[6,6] -phenyl-C61-butyric acid methyl ester (P3HT:PCBM) bulk-heterojunction solar cells by incorporating gold nanorods (GNRs), with tunable densities and orientations, into the anodic layer. GNRs with an aspect ratio of approximately 4, confirmed by transmission electron microscopy, were synthesised via a seed-mediated growth route and integrated by vertically deposition beneath the anodic layer using a simple solution-based process for various durations (10-60 min). Deposition time controlled the density and alignment of nanorods, influencing light-harvesting and charge-generation efficiencies. Optical, morphological, and electrical characterizations confirmed that this approach provided reproducible plasmonic enhancement without the need for sophisticated nanofabrication. The optimal performance occurred after 30-min deposition, yielding a 42% increase in power-conversion efficiency due to a 30.0% and 10% improvement in fill factor and short-circuit current density, respectively, compared with control devices. Spectral analysis revealed an 11% absorption increase in the active layer due to localized surface plasmon resonance and forward-scattering. This simple plasmonic-enhancement method improves optical absorption and charge generation without complex lithography or high-cost materials, demonstrating that plasmonic GNRs can serve as an effective light-management and charge-generation strategy for improving the efficiency of polymer:fullerene organic solar cells.