Fabrication of plasmon enhanced amorphous silicon solar cells using RF magnetron sputtering
Date
2019
Authors
Kumalo, Sandile
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Abstract
Renewable energy continues to attract intensive interest as a possible alternative to fossil fuel based energy sources due to its merits which are abundance, clean and geographically unlimited natural resources. The increased concerns of the harmful effects to the environment by fossil fuels has prompted a massive drive for photovoltaic based energy solutions. The current available solar technologies,thin film solar cells,have the potential of reducing production costs. However,the low photo conversion efficiency slows the irrapid integration into the energy mix. In this work,we explore sophisticated light management strategiesofsiliconbasedthinfilmsolarcellstoenhancetheirphotoconversioneciency. These strategies ensure the enhancement of absorption of the complete solar spectrum, also reduced materials costs and a strongly reduced emission of greenhouse gases. The work involved fabricating and designing three significant layers of a hydrogenated amorphous silicon (a-Si:H) solar cell device, and integrating plasmonic nanoparticles in the commercial a-Si device to enhance optical absorption through Surface Plasmon Resonance (SPR). The project also involved several strategies to increase the conversion effciency of a commercial a-Si standard device for comparative studies. Recent approaches in the improvement of light absorption in solar cells were due to the use of plasmonic nanoparticles. It is well known theoretically as well as experimentally that metallic nanostructures have a strong interaction with light. This interaction allows remarkable control of the trapping and propagation of the photons in the intrinsic layer of thin film devices. For such a plasmon enhanced device to be economically viable and commercialised, the nanoparticles must be silver (Ag) and gold (Au), and the method used for the deposition must be carried out at temperatures lower than the ones used for the fabrication of a-Si:H layers. Thus the RF magnetron sputtering technique in combination with ion implantation of each a-Si layers to form n and p-type a-Si was used to fabricate the three layers of an a-Si:H device. The architecture of the device is in a n-i-p or p-i-n sequence of doped semiconductor layers and each layer is fabricated using sputtering. Then Ag and Au nanoparticles were integrated into the commercial a-Si reference device. The devices are characterized for power conversion efficiency and I-V characteristics.
Description
A dissertation submitted to the Faculty of Science,University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Masters of Science, May 2019