Over the last five years, a dramatic expansion of renewable energy from Photovoltaic (PV) solar cells has been witnessed. This expansion is due in part to wafer based silicon solar cells. Crystalline silicon solar cells currently dominate the PV market because of their low cost per watt of electricity production. In order for silicon solar cells to continue to govern the market, efficiency improvements and cost reductions must be made. This work focuses on both cost reduction and efficiency improvements, for wafer based silicon solar cells. The main aim of the work was to produce a thin monocrystalline wafer based silicon solar cell. A large proportion of the cost of conventional monocrystalline solar cells is related to the use of high purity silicon substrates. By producing a cell that uses less silicon, significant cost savings can be made. Conventional wafering techniques used in industry are reaching their limit for thin wafer production. The method adopted in this work uses a simple silicon exfoliation technique capable of producing ultrathin silicon foils. A fully operational solar cell was fabricated from a 40mum exfoliated silicon foil. The thin wafer based silicon solar cell was more than four times thinner than a commercially produced equivalent. The work investigated a variety of principles related to the exfoliation and the suitability of the technique for thin photovoltaic devices. By using a thin exfoliated substrate, conventional anti-reflective (AR) suppressing processes could prove problematic. Experiments were conducted into finding an alternative technique to match the performance of the conventional AR process. The formation of porous silicon (PSi) on the surface of a silicon substrate was found not only to match the commercial process, but to exceed it. With a porous silicon layer, reflectivity was suppressed to just 6.68%. The technique could be applied to both thin silicon solar cells and conventional thicker wafer based cells. The reflectivity suppressive layer could be fabricated in a single simple processing step. Investigation was also focused upon the top contact for silicon solar cells. As the top of the cell is responsible for current collection and light absorption, large electrical contacts shade the cell resulting in a decrease in efficiency. Silver nanowires (AgNWs) were successfully analysed and deposited onto standard silicon solar cell top contacts as an enhancement coating. Such a coating was found to improve the collection ability of the top contact without causing a significant increase in shading loss. The use of an optimised AgNW coating can increase cell efficiency by as much as 37%.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:678623 |
| Date | January 2014 |
| Creators | Blayney, Gareth John |
| Publisher | Swansea University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | https://cronfa.swan.ac.uk/Record/cronfa42531 |
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