Electrochemical photovoltaic cell

Al-Dhafiri AM, Russell GJ, Woods J (1991) Electrochemical control of the CuxS phase in CuxS-CdS photovoltaic cells. Semicond Sci Technol 6 983-988... 

Langmuir ME, Parker MA, Rauh MD (1982) Electrochemical photovoltaic cells based on n-GaAs and the triiodide/iodide redox couple in acetonitrile. J Electrochem Soc 129 1705-1710... 

Antonucci V, Arico AS, Giordano N, Antonucci PL, Russo U, Cocke DL, Crea F (1991) Photoactive screen-printed pyrite anodes for electrochemical photovoltaic cells. Sol Cells 31 119-141... 

Tien HT, Chen JW (1989) Hydrogen generation from artificial sea water in a semiconductor septum electrochemical photovoltaic cell. Photochem Photobiol 49 527-530... 

Tien HT, Chen JW (1990) Hydrogen production from water by semiconductor septum electrochemical photovoltaic cell using visible light. Int J Hydrogen Energy 15 563-568... 

As it has been described in various other review articles before, the conversion efficiencies of photovoltaic cells depend on the band gap of the semiconductor used in these systems The maximum efficiency is expected for a bandgap around Eg = 1.3eV. Theoretically, efficiencies up to 30% seem to be possible . Experimental values of 20% as obtained with single crystal solid state devices have been reported " . Since the basic properties are identical for solid/solid junctions and for solid/liquid junctions the same conditions for high efficiencies are valid. Before discussing special problems of electrochemical solar cells the limiting factors in solid photovoltaic cells will be described first. 

The electrochemical cell can again be of the regenerative or electrosynthetic type, as with the photogalvanic cells described above. In the regenerative photovoltaic cell, the electron donor (D) and acceptor (A) (see Fig. 5.62) are two redox forms of one reversible redox couple, e.g. Fe(CN)6-/4 , I2/I , Br2/Br , S2 /S2, etc. the cell reaction is cyclic (AG = 0, cf. Eq. (5.10.24) since =A and D = A ). On the other hand, in the electrosynthetic cell, the half-cell reactions are irreversible and the products (D+ and A ) accumulate in the electrolyte. The most carefully studied reaction of this type is photoelectrolysis of water (D+ = 02 and A = H2)- Other photoelectrosynthetic studies include the preparation of S2O8-, the reduction of C02 to formic acid, N2 to NH3, etc. 

Ginley, D. S. 1999. Nanoparticle-derived contacts for photovoltaic cells Proc.— Electrochem. Soc. 99-11 103-109. 

The covalent chemistry of fullerenes has developed very rapidly in the past decade in an effort to modify fuUerene properties for a number of applications such as photovoltaic cells, infrared detectors, optical limiting devices, chemical gas sensors, three-dimensional electroactive polymers, and molecular wires [8, 25, 26, 80-82]. Systematic studies of the redox properties of Cgo derivatives have played a crucial role in the characterization of their unique electronic properties, which lie at the center of these potential applications. Furthermore, electrochemical techniques have been used to synthesize and separate new fullerene derivatives and their isomers as well as to prepare fullerene containing thin films and polymers. In this section, to facilitate discussion of their redox properties, Cgo derivatives have been classified in three groups on the basis of the type of attachment of the addend to the fullerene. In group one, the addends are attached via single bonds to the Cgo surface as shown in Fig. 6(a) and are referred to as singly bonded functionalized derivatives. The group includes... 

Similar photovoltaic cells can be made of semiconductor/liquid junctions. For example, the system could consist of an n-type semiconductor and an inert metal counterelectrode, in contact with an electrolyte solution containing a suitable reversible redox couple. At equilibrium, the electrochemical potential of the redox system in solution is aligned with the Fermi level of the semiconductor. Upon light excitation, the generated holes move toward the Si surface and are consumed for the oxidation of the red species. The charge transfer at the Si/electrolyte interface should account for the width of occupied states in the semiconductor and the range of the energy states in the redox system as represented in Fig. 1. 

It has then to be concluded that the charge transfer in the ferrocene/ferroci-nium couple in this specific solvent is a fast process at the timescale of the hole diffusion in the semiconductor space charge layer. However, at the present time, it seems that the constraints arising from the construction of a perfectly tight device will hinder the development of these electrochemical photovoltaic cells. 

The low stability of the magnesium porphyrins has precluded most potential applications. Other metallotetrapyrroles have found industrial uses for oil desulfurization, as photoconducting agents in photocopiers, deodorants, germicides, optical computer disks, semiconductor devices, photovoltaic cells, optical and electrochemical sensing, and molecular electronic materials. A few scattered examples of the use of Mg porphyrins in nonlinear optical studies have appeared" and magnesium phthalocyanines have been used in a few studies as semiconductor or photovoltaic materials" " One of the few... 

Electrochemical photovoltaic cells. In an electrochemical photovoltaic cell, the two electrode reactions are the inverse of each other R + (anode) and... 

Table 7.1. Typical examples of semiconductor-based electrochemical photovoltaic cells operating in an aqueous medium...

This volume, based on the symposium Photoeffects at Semiconductor-Electrolyte Interfaces, consists of 25 invited and contributed papers. Although the emphasis of the symposium was on the more basic aspects of research in photoelectrochemistry, the covered topics included applied research on photoelectrochemical cells. This is natural since it is clear that the driving force for the intense current interest and activity in photoelectrochemistry is the potential development of photoelectrochemical cells for solar energy conversion. These versatile cells can be designed either to produce electricity (electrochemical photovoltaic cells) or to produce fuels and chemicals (photoelectrosynthetic cells). 

Figure 33. Dye (D) sensitized electrochemical photovoltaic cell based on a wide bandgap semiconductor. Reprinted from R. Memming, Semiconductor Electrochemistry, Wiley-VCH Verlag GmbH, Weinheim (2001). Copyright 2001 with permission from Wiley-VCH Verlag GmbH.

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