Rear Located plasmonic Structures for Light Trapping in Solar Cells

Photovoltaics are a key technology which can meet rising global demand for clean energy. However, significant improvements in performance are required to maximize their utilization of incoming solar radiation. Plasmonics show promise to improve light trapping in cells, taking advantage of properties of nanoscale metals. Plasmonic light trapping allows for significant increases to the path-length of light through a solar cell, increasing the chance of absorption. Since metal forms an integral part of solar cell designs, the motivation of this work is to investigate metal-based structures with potential to improve cell performance in thin-film solar cells without adding to the cost.In this thesis, rear-located reflectors are investigated, comprising arrays of metal nanoparticles, or nano-textured metal films. 3D simulations explore various aspects of these structures’ performance, including scattering and absorption, the angle at which they scatter light, electric field profiles, and idealised photocurrent. Key design parameters are identified and optimised. This thesis also examines the underlying mechanisms of their performance enhancement.Beyond investigating the design of plasmonic rear reflectors, the impact their deployment in more realistic environments is also considered. Ageing of metal nanoparticles exposed to atmosphere is found to lead to tarnishing which can reduce the performance enhancement offered by such structures and needs to be considered in their design.Overall, the nano-textured reflectors investigated show potential to provide significant performance enhancements over a standard planar rear mirror, and in some cases to the metal nanoparticles. They also have the additional advantage of potentially serving as a cell’s rear contact. Particularly promising enhancements are shown for thinner cells. Parasitic absorption losses in such metal rear reflectors is investigated. Large angle scattering at resonant wavelengths is found to provide performance enhancements that significantly outweigh the negative impacts of increased parasitic absorption in such textured metal films