Title:
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Reducing the cost of crystalline silicon solar cells by using fluorescent collectors
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This research is concerned with overcoming the first obstacle, by aiming to increase the fundamental understanding of photon transport in fluorescent collectors, and to explore the feasibility of employing these devices to improve the energy collection of crystalline silicon (c-Si) solar cells. This thesis presents the theoretical and experimental results obtained during the development and characterisation of fluorescent collectors and c-Si solar cells. Two different structures of c-Si cells were successfully fabricated. The first type was a wafer-based c-Si solar cell with an n⁺/p/p⁺ structure, and the second type was a thin-film c-Si solar cell whose structure can exploit the benefit of fluorescent concentration. Characterisation of the wafer-based device revealed the presence of a heavily doped region near the front surface. To gain a deeper insight into the influence of this layer, a theoretical model was developed and used to analyse the collection efficiency of minority carriers within the base and emitter regions of the device. A method for preparing fluorescent collector plates was established by spin-coating dye-doped PMMA (Polymethylmethacrylate) on glass slides. An optical characterisation technique for determining re-absorption loss of the fluorescent collectors was developed and used to evaluate the performance of the fluorescent collectors based on Rhodamine 6G. The validity of this approach was verified by comparing the results with theoretical solutions, derived using a model adapted from Weber and Lambe's theory. The two different collector structures were developed and characterised for their electrical performance. For structures based on conventional cells, the experimental results showed a significant increase in the output current at an optimum dye concentration. The hybrid thin-film fluorescent collector was also successfully fabricated.
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