Dye Sensitized Solar Cells K Kalyanasundaram Pdf Download [2021]
Dye Sensitized Solar Cells K Kalyanasundaram Pdf Download ::: https://tlniurl.com/2teKFW
Several forms of thin-film solar cells are being examined as alternatives to silicon-solar cells-one of the most promising technologies is the dye-sensitized solar cell (DSC), with proven efficiencies that approach 11%. This book, which provides a comprehensive look at this promising technology, aims to provide both a graduate level text that bring
How to cite this article: Kakiage, K. et al. Achievement of over 1.4 V photovoltage in a dye-sensitized solar cell by the application of a silyl-anchor coumarin dye. Sci. Rep. 6, 35888; doi: 10.1038/srep35888 (2016).
Electrochemical impedance spectroscopy (EIS) is one of the most important tools to elucidate the charge transfer and transport processes in various electrochemical systems including dye-sensitized solar cells (DSSCs). Even though there are many books and reports on EIS, it is often very difficult to explain the EIS spectra of DSSCs. Understanding EIS through calculating EIS spectra on spreadsheet can be a powerful approach as the user, without having any programming knowledge, can go through each step of calculation on a spreadsheet and get instant feedback by visualizing the calculated results or plot on the same spreadsheet. Here, a brief account of the EIS of DSSCs is given with fundamental aspects and their spreadsheet calculation. The review should help one to develop a basic understanding about EIS of DSSCs through interacting with spreadsheet.
So far we have seen that the imaginary part of the impedances for different combination of resistances and capacitors showed negative values and the spectra appeared in the first quadrant of the complex plane. However, the imaginary parts sometimes take positive values and thus the spectra appear in both first and forth quadrants due to the inductance of the contact wire, which often produces a tail at high frequencies (Figure 5(a)) [2]. On the other hand, impedances of several types of solar cells show similar phenomenon, however at low frequency region, as a loop that forms an arc in the fourth quadrant (Figure 5(b)), which is attributed to specific adsorption and electrocrystallization processes at the electrode [2, 4].
Dye-sensitized TiO2 solar cells, DSSC, are a promising alternative for the development of a new generation of photovoltaic devices. DSSC are a successful combination of materials, consisting of a transparent electrode coated with a dye-sensitized mesoporous film of nanocrystalline particles of TiO2, an electrolyte containing a suitable redox-couple and a Pt coated counter-electrode. In general, Ru bipyridyl complexes are used as the dye sensitizers. The light-to-energy conversion performance of the cell depends on the relative energy levels of the semiconductor and dye and on the kinetics of the electron-transfer processes at the sensitized semiconductor electrolyte interface. The rate of these processes depends on the properties of its components. This contribution presents a discussion on the influence of each of the materials which constitute the DSSC of the overall process for energy conversion. An overview of the results obtained for solid-state dye-sensitized TiO2 solar cells assembled with polymer electrolytes is also presented.
Dye-sensitized TiO2 solar cells, DSSC, are a promising alternative for the development of a new generation of photovoltaic devices. DSSC are a successful combination of materials, consisting of a transparent electrode coated with a dye-sensitized mesoporous film of nanocrystalline particles of TiO2, an electrolyte containing a suitable redox-couple and a Pt coated counter-electrode. In general, Ru bipyridyl complexes are used as the dye sensitizers. The light-to-energy conversion performance of the cell depends on the relative energy levels of the semiconductor and dye and on the kinetics of the electron-transfer processes at the sensitized semiconductor electrolyte interface. The rate of these processes depends on the properties of its components. This contribution presents a discussion on the influence of each of the materials which constitute the DSSC of the overall process for energy conversion. An overview of the results obtained for solid-state dye-sensitized TiO2 solar cells assembled with polymer electrolytes is also presented.
Solar energy conversion and storage can be achieved by photo-electrochemical processes, and photosynthesis is the most successful example of this approach. A strategy for chemically-based solar energy conversion is semiconductor liquid junction solar cells, for instance n-CdSe in aqueous Fe(CN)63-/4- or poly-chalcogenides (Figure 1). When illuminated, the semiconductor collects photons with energy that exceeds the energy gap between the valence and the conduction bands. It promotes the separation of electron/hole pairs, i.e., an electron is promoted from the valence band (VB) to the conduction band (CB), leaving behind a hole, a positively charged VB vacancy. While the electron moves away from the interface and toward the external circuit, the hole migrates to the semiconductor solution interface. At the interface, the hole oxidizes an electron donor in solution. The oxidized molecule diffuses through solution to the counter-electrode, where it can be reduced, completing the circuit. Thus, only electricity is produced and no net chemical reaction occurs since every interfacial oxidation at the photoelectrode is compensated by an interfacial reduction reaction at the counter-electrode. Direct energy conversion relies on the semiconductor material, which can absorb a fraction of the solar spectrum depending on its bandgap energy (Ebg). Unfortunately, many materials with adequate bandgaps are susceptible to photocorrosion, due to destructive hole-based reactions. Also, the semiconductors less susceptible to photocorrosion, such as metal oxides like TiO2 and SnO2, exhibit a too large bandgap to permit significant collection of visible light.2,3
Photoelectrochemical cells based on dye-sensitized semiconductor electrodes also include solutions containing a suitable redox couple and a counter-electrode. The illumination leads to excitation of the dye to an electronically excited state which is quenched by electron-transfer to the CB of the semiconductor, leaving the dye in an oxidized state. The oxidized dye is reduced by the electron donor present in the electrolyte. The electrons in the CB are collected, flow through the external circuit to arrive at the counter-electrode, where they cause the reverse reaction of the redox mediator. Thus, the photoelectrochemical cell is also regenerative and the process leads to direct conversion of sunlight into electricity. If only the above reactions took place, the solar cell would be stable, delivering photocurrent indefinitely. The maximum photovoltage, at open circuit potential (VOC), is the difference between the Fermi level (CB) of the semiconductor under illumination and the redox potential of the mediating redox couple. The photocurrent yield depends on the spectral and redox properties of the dye, its excited state lifetimes, the efficiency of charge injection, the ionic conductivity of the electrolyte and the properties of the semiconductor electrode to collect and channel the electrons through the external circuit.3,4
In earlier studies of photoelectrochemical cells, just single crystals or flat electrodes of polycrystalline films of tin oxide or titanium oxide were used. In spite of the efficient electron injection into the semiconductor, the light harvesting efficiency was very small and the efficiencies of the solar cells were extremely low, below 1%.2,4,6 At the beginning of the nineties, in the laboratories of Grätzel, in Lausanne, Switzerland, the planar semiconductor electrode was replaced by a porous film of nanocrystalline TiO2 particles deposited onto a conducting glass electrode. The enormous surface area of the nanocrystalline TiO2 film allowed high light harvesting efficiency and the overall efficiency for solar energy conversion increased by an order of magnitude.2,4-8 The regenerative dye-sensitized TiO2 photoelectrochemical cell attracted the attention of several researchers. A photoelectrochemical cell was patented by Grätzel in 1990 (US Patent 4,927,721) and, after that, more than 800 patents were registered at The United States Patent and Trademark Office.9 A schematic representation of a nanocrystalline dye-sensitized TiO2 solar cell, DSSC, and the processes that occur during cell operation are depicted in Figure 2.
The most efficient DSSC that has been reported consisted of a porous anatase TiO2 film, deposited onto a transparent electrode, sensitized by the dye RuII(2,2'-bipyridyl-4,4'-dicarboxylate)2-(NCS) 2 (also called N3 dye), an acetonitrile electrolyte with the redox couple I-/I3- and a Pt counter-electrode, as represented in Figure 2. The photocurrent measured at ca. 100 mW cm-2 of simulated solar intensity (AM 1.5) was 20 mA cm-2, the open circuit voltage, VOC, was 0.7 V, and the overall efficiency of the cell for light to electrical conversion was hglobal 10%. The cell performance was still better under diffuse daylight, hglobal 12%, revealing that the DSSC is less sensitive to light intensity variations than conventional photovoltaic devices, which is an important advantage for application in consumer electronic devices.4-8,10
Another alternative to make flexible DSSC consists of depositing a film of TiO2 particles onto flexible electrodes from the usual suspension, exposing the film to UV radiation for few minutes and heating them at 140-150 oC.26 This treatment promotes the photodegradation of organic compounds, allowing the elimination of most of the organic residues from the TiO2 suspension. The resulting films were mechanically stable, presented an intense adsorption of the dye and relatively good performance in solid-state, flexible TiO2/dye solar cells assembled with a polymer electrolyte. These cells, with an active area of 1 cm2, exhibited short-circuit current ISC = 60 mA cm2, open circuit potential VOC = 0.7 V and hglobal = 0.32% under 10 mW cm2 (hglobal = 0.23% under 100 mW cm2). The efficiency of these cells also decayed with time, but cell performance loss was associated with an increase in the series resistance of the cell, as verified by electrochemical impedance measurements. This effect was not so evident for cells prepared by a similar procedure using glass electrodes, revealing that the flexible electrode creates a large series resistance in the solar cell. However, the results obtained for flexible DSSC can be considered very promising for developing solar cells with a lower cost and broader applicability.26 153554b96e
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