Design, fabrication and characterization of plasmon-enhanced dye-sensitized solar cells (Master thesis)

Μυταφίδης, Χρήστος Κ.

Motivated by the ever-increasing world energy demands of our times and the depletion of readily accessible fossil fuels, the investigation for alternative energy sources has become vitally important in terms of sustainability. Particularly the renewable solar energy, although its great potential as a renewable source, it is crucial for the respective solar production systems to have a competitive cost and performance compared to conventional energy sources. Dye-sensitized solar cells (DSSCs) have entered public view as significant breakthroughs in this field (O'Regan & Grätzel, 1991) and garnered more and more research attention at present, as they meet the very attractive properties of low cost and simple manufacturing processes, while at the same time having advantageous characteristics over conventional solar cells (e.g., lightweight, flexible, low toxic, and good performance in diverse light conditions (M. Grätzel, 2006)). A DSSC typically consists of a several microns thick semiconductor film (e.g., TiO2, ZnO, SnO2) served as a photoanode that is coated or grown on a conductive substrate, a sensitizer (e.g., metal-complex or organic dyes) an electrolyte (e.g., 𝐼𝐼3−/𝐼𝐼− redox couple) between the sensitizer and the counter electrode, and the counter electrode (e.g., platinum, carbon) deposited on another conductive substrate. The incident solar radiation on the photoanode causes photo-excitation of the absorbed dye molecules to generate excited electrons which are subsequently injected into the conduction band of the semiconductor and shuttled to the external circuit through the conductive substrate, producing an electric current. The initial state of the dye is subsequently restored by electron donation from the redox electrolyte. Each part of the device strongly determines the cost and efficiency of DSSCs. In recent years, multiple studies have been published on the modification of each component with the ultimate goal of improved applied and practical applications. Areas of interest have included the development of nanostructured semiconductor photoanodes with effective architectures for high dye loading and fast electron transport, the exploitation of versatile sensitizers with strong visible light harvesting ability, the utilization of redox electrolytes for efficient hole transport, the optimization of the platinum counter electrode as well as the development of other equivalent alternatives at lower costs (Tetreault & (W. & Ma, 2012; S. Zhang et al., 2013). A new milestone for solid-state mesoscopic TiO2 solar cells sensitized with lead iodide perovskite was reported to achieve an impressive power conversion efficiency of more than 20% (N.G. Park, 2013; Shin et al., 2017). In this thesis, the experimental results of the design and development of dye-sensitized solar cells are presented, in which, mesoporous films of nanocrystalline titania (TiO2) were spin-coated as a semiconductor photoanode and subsequently sensitized with organic and natural dyes. The redox couple of iodide electrolyte was used (𝐼𝐼3−/𝐼𝐼−) where the contribution and functionality of the following counter electrodes were investigated: (i) platinum, (ii) platinum & carbon, (iii) carbon. Additionally, the amplification of the photocurrent by light reflection after placing a high reflectance surface under the cells was experimentally investigated. Moreover, the contribution of plasmonic nanoparticles to the photovoltaic performance of DSSCs was studied computationally and bibliographically as a function of the experimental results. A remarkable result of this thesis was achieved as a product of the sensitization with the natural dye of Blueberries and a combinatorial platinum/carbon counter electrode, which DSSC achieved efficiencies of 3.09% and 3.77% after the measurements with the highly reflective surface and the introduction of the gold nanoparticles (AuNPs), respectively. In addition to the results of this work, there are highlighted some noteworthy aspects for future research into the corresponding solar cell sector.
Institution and School/Department of submitter: Πανεπιστήμιο Ιωαννίνων. Πολυτεχνική Σχολή. Τμήμα Μηχανικών Επιστήμης Υλικών
Subject classification: Φωτοβολταϊκά δυναμικά συστήματα
Keywords: Φωτοευαισθητοποιημένα ηλιακά κύτταρα,Πλασμονικά νανοσωματίδια,Φωτοβολταϊκά,Υλικά συγκομιδής ενέργειας,Dye-sensitized solar cells,Plasmonic nanoparticles,Photovoltaics,Energy harvesting materials
Appears in Collections:Διατριβές Μεταπτυχιακής Έρευνας (Masters)

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