Fluorine-doped tin oxide electrode

Figure 10.17. (a) Schematic diagram of the nanowire dye-sensitized solar cell. Light is incident through the bottom electrode, (b) SEM cross section of a solution-fabricated ZnO nanowire array on fluorine-doped tin oxide. The wires are in direct contact with the substrate. Scale bar, 5 pm. Reproduced from Ref. 41, Copyright 2005, with permission from the Nature Publishing Group. 

To detail DSSC technologies, Fig. 18.1 illustrates the modus operandi of DSSCs. Initially, light is absorbed by a dye, which is anchored to the surface of either n- or p-type semiconductor mesoporous electrodes. Importantly, the possibility of integrating both types of electrodes into single DSSCs has evoked the potential of developing tandem DSSCs, which feature better overall device performances compared to just n-or p-type based DSSCs [19-26]. Briefly, n-type DSSCs, such as TiOz or ZnO mesoporous films, are deposited on top of indium-tin oxide (ITO) or fluorine-doped tin oxide (FTO) substrates and constitute the photoanodes. Here, charge separation takes place at the dye/electrode interface by means of electron injection from the photoexcited dye into the conduction band (cb) of the semiconductor [27,28]. A different mechanism governs p-type DSSCs, which are mainly based on NiO electrodes on ITO and/or FTO substrates... 

Substrates DME = dropping mercury electrode FTO = fluorine-doped tin oxide G = graphite GC = glassy carbon GrC = graphic carbon ITO = indium tin oxide-coated glass SC = single crystals SS = stainless steel TCO = transparent conducting oxide VC = vitrious carbon. Miscellaneous ECALE = electrochemical atomic layer epitaxy ED = electrodeposition ML = monolayer RT = room temperature SMD = sequential monolayer deposition V = vacuum. 

Examples of the application of solid state electrochemistry to identifying dyes in textile samples can be provided. Thus, Fig. 2.17 compares the square wave voltam-mograms of (a) saffron blank, and (b) sample from a Tibet temple, attached to fluorine-doped tin oxide (FTO) electrodes immersed into acetate buffer. After initiating the potential scan at -0.85 V in the positive direction, two separated oxidation... 

Figure 48. Scheme of a photoelectrochemical cell constituted by two conducting glass electrodes (FTO = fluorine doped tin oxide) one side coated with a film of Ti02, as the semiconducting photoactive interface and a redox mediator (la/I ) dissolved in methoxipropionitrile. A thin platinum film is also employed to improve the electrical contact with the second electrode. 

Direct electron transfer between CCP and an electrode was first reported (45) for the nonphysiological one-electron reduction and reoxidation of ferric CCP at fluorine-doped tin oxide. Overpotentials of around 0.5 V were required to drive this electrode reaction in either direction at measurable rates. A more successful approach to direct electroreduction of compound I, described by Armstrong and Lannon (46), employed edge-plane graphite electrodes in the presence of... 

At the same time, SWNT can be used at the top electrode (that needs to be transparent) as a replacement for the currently used thin films that are also electrical conductors. Typical conductive thin films used today are oxides such as fluorine-doped tin oxide (FTO), Al-doped zinc oxide, and the indium tin oxide (ITO) mentioned above. The disadvantages of these oxide films are that they require expensive deposition procedures at high vacuum, they have poor mechanical properties, and they are not transparent in the infrared. Another interesting difference is that transparent oxide conductors are n-type semiconductors. By contrast, nanotube networks act as p-type semiconductors, which could lead to new designs. 

The electrodes used in the ECDs are dependent on the type of device absorptive/transmissive (window type) or absorptive/reflective. Typical electrodes are the transparent conductors such as ITO, fluorine-doped tin oxide (Sn02 F), and PEDOT/PSS for the absorptive/transmissive window-type ECDs and reflective metals such as gold in reflective display-type devices. Single-walled carbon nanotubes (SWNTs) have emerged as an alternative to transparent electrodes such as ITO, with comparable transparency in the visible region and far superior transparency in the wavelength range of 2-5 p,m [258]. 

This device gave an incident-photon-to-collected-electron efl ciency of 12.1% and a power conversion efl ciency of 0.8% under monochromatic irradiation [279]. Single-polymer-layer photovoltaic devices using polybithiophene (PBT) thin films and fluorine-doped tin oxide substrate have also been constructed (Fig. 7.22). As well as the difference in the work functions of the electrodes, the high organization of the molecular dipoles in PBT yielded an open-circuit potential of 2 V when an aluminum top contact was used [279]. 

FTO fluorine-doped tin oxide films, PVP poly(4-vinylphenol), Au-PVS/N-PANI gold electrode modified with LbL film of poly(vinyl sulfonic acid) (PVS) and nanostructurated polyaniline (N-PANI)... 

The most commonly encountered TCO electrodes, typically studied as thin films, are antimony-doped tin oxide (ATO) or fluorine-doped tin oxide (FTO), ITO, titanium oxide (anatase or rutile, Ti02), and zinc oxide (ZnO) [19], There are also some recently reported trinary and ternary oxides based on modifications of ITO, zinc-indium tin oxide, ZITO or IZTO, for example, which may become more popular with time as electrodes for solution-based redox chemistry and as anodes in devices such as OLEDs and OPVs [7], These new tailored composition oxides may exhibit higher stability, higher work functions, and/or a greater variety of surface sites with more possibilities for chemical modification. 

The active layer of the DSSCs consists of a mesoporous nanocrystalline metal oxide (typically titanium dioxide or zinc oxide) deposited on fluorine-doped tin oxide (FTO) electrode and covered with some organic or organometaUic dye. The dye molecules (D) absorb light while populating... 

Brinker C.J., Scherer G.W. Sol-Gel Science. New York Academic Press, 1990 Cachet C., Cachet H., Jousseaume B., Toupance T., Vivier V. Electrochemistry of a new carbon-rich fluorine-doped tin oxide (CFTO) material as a powder electrode in chloride electrolytes. Electrochim. Acta 2002 47 1385-1394... 

The system consists of five functional layers, which are located between two glass or plastic substrates. Each plate is coated with a thin transparent conductive electrode (TCE), usually a doped form of tin oxide e.g., fluorine doped tin oxide (FTO Sn02 F) or Sn-doped indium oxide (ITO In203 Sn). One ofthe TCE is coated with an electrochromic coating (EC-layer), the other with a coimter electrode (CE layer). Both layer systems are separated by an ionic conductive electrolyte with very low electronic conductivity. In order to have high diffusion coefficients and fast kinetics, the ions should be small, therefore protons (H" ) or lithium (Li ) are preferred. The electrical contacts are attached at the TCE coatings. 

Fig. 5.7 SEM images of anatase Ti02 electrodes derived from electrospun nanofibers (a) after calcining the as-spun Ti02/PVAc composite nanofibers (as shown in the inset, each Ti02 fiber consisted of a bundle of fibrils roughly 20 nm in diameter), (b) after treatment with an aqueous TiCLt solution to deposit an additional layer of rutile to improve the performance, (C) schematic of a nanorod-on-nanoparticle electrode prepared by mechanically grinding electrospun Ti02 nanofibers and then electrospraying the resultant Ti02 nanorods onto a fluorine-doped tin oxide (FTO) substrate, and (d) SEM image of the cross-section of such an electrode...

The average diameter of PANI CSA-PLA nanofibers determined from the SEM images was about 200 nm, with a standard deviation of about 100 nm and length up to several hundred micrometers (Fig. 5.10). The as-electrospun PANI CSA-PLA nanofibers were stacked and bonded with the substrate firmly, resulting in an interconnected nanofibrous network with a thickness of about 2 mm. This network structure was in favor of the infiltration of electrolyte and further promotes the electrocatalytic activity for the reduction of 13 ions. The nanofibers were directly deposited on rigid fluorine-doped tin oxide (FTO) and also flexible indium tin oxide-coated polyethylene naphthalate (PEN) substrates to obtain the counter electrodes, which is close to that of sputtered Pt-based DSSCs. 

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