In thin film solar cells made as planar structures, the absorption of solar light and hence, the solar conversion efficiency, is heavily determined by the position and orientation of the sun. One way to overcome this is to use solar cell geometries that could better absorb sunlight from different angles. One potential geometry is a hollow cylinder, which has the ability to better absorb the sun’s rays incident at various angles due to the light trapping nature of the cylindrical geometry. If such solar cells could be fabricated inside polymer tubes with micrometer diameters, many potential applications built around non-woven or woven textiles could be realized. Here we investigate the deposition of homogeneous thin metallic films inside hollow polymer cylinders using the process of chemical bath deposition (CBD). Although films deposited via CBD have been studied extensively, mechanisms to achieve high quality deposition inside hollow cylinders are still not well understood. The objective of this project was to deposit a smooth, homogeneous silver film inside a hollow cylindrical structure using varying flow rates. The early stage film growth for very short deposition times was observed by the localized surface plasmon resonance of the silver nanoclusters via absorption spectra along the length of the tube. For longer deposition times, silver films formed and were analyzed for their morphology, thickness, roughness, and resistance using a combination of optical microscopy, scanning electron microscopy, and two-probe conductivity. The findings from this study showed that deposition under flow with different Reynolds numbers had a strong influence on the morphology and electrical resistance of the deposited films.
KEYWORDS: Thin-films; Chemical Bath Deposition; Nanoparticles; Solar Cells; Silver
Thermodynamic limit to photonic-plasmonic light-trapping in thin films on metals