Photoelectrochemical photovoltaic cell

R. E. Malpas and B. Rushby, The stability of two-layer ferrocene/polypyrrole-coated n-Si electrodes in aqueous photoelectrochemical photovoltaic cells, J. Electroanal. Chem. 157, 387, 1983. 

Assuming a quantum efficiency of unity, then /e is the photocurrent of the cell. The maximum conversion efficiency is defined by Eq. (11.5). It can be calculated for semiconductors of different bandgaps from Eqs. (11.5) and (11.12). The results are presented in Fig. 11.9. The highest efficiency is 28 % at g = 1.2 eV. This calculation is valid for solid state photovoltaic devices (p-n junction, Schottky junction) as well as for a photoelectrochemical photovoltaic cell. 

A photoelectrochemical photovoltaic cell was fabricated by dipping PA into an aqueous sodium polysulfide The cell gave = 0.3 V and = 40 pA cm under AM 1 illumination. A similar photoelectrochemical cell was fabricated with tmns- k which was dipped into an aqueous methylviologen (MV " ) solution... 

Fig> 23-15 Photoelectrochemical photovoltaic cell using poly(acetylene) as an... 

Metal oxide electrodes have been coated with a monolayer of this same diaminosilane (Table 3, No. 5) by contacting the electrodes with a benzene solution of the silane at room temperature (30). Electroactive moieties attached to such silane-treated electrodes undergo electron-transfer reactions with the underlying metal oxide (31). Dye molecules attached to sdylated electrodes absorb light coincident with the absorption spectmm of the dye, which is a first step toward simple production of photoelectrochemical devices (32) (see Photovoltaic cells). 

Gutierrez MT, Salvador P (1987) Photoelectrochemical characterization and optimization of a liquid-junction photovoltaic cell based on electrodeposited CdSe thin films Influence of anneaUng and photoetching on the physical parameters determining the cell performance. Sol Energy Mater 15 99-113... 

Dhere, N.G. and Jahagirdar, A.H., Photoelectrochemical water splitting for hydrogen production using multiple bandgap combination of photovoltaic cell and thin-film-photocatalyst,... 

Photoelectrochemical semiconductor cells are used to convert photon energy into chemical substances or into electricity, the former is a photodectrolytic cell and the latter is a photovoltaic cell. A photoelectrochemical semiconductor cell consists of either a pair of metal and semiconductor electrodes or a pair of two semiconductor electrodes. 

The final two chapters deal with applications (in the scientific as well as commercial sense) of CD films. As already mentioned, photovoltaic cells is the one subject that has given CD a push in the last decade, while photoelectrochem-ical cells was probably the main driving force for such studies in the decade before that. Chapter 9 deals with Photovoltaic and Photoelectrochemical Properties. 

A large number of studies on CD have been driven by two related potential uses photoelectrochemical (PEC) cells, mostly the earlier studies, and, more recently, photovoltaic (PV) cells. This chapter is devoted to these two topics where CD films have been used. 

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). 

Another interesting work is the recent report by Licht et al [72, 75, 94]. Although the system they studied was not a strict photoelectrochemical one, since the photovoltaic system was separated from the water electrolyser, their study is of general interest for the water oxidation field. The photovoltaic cell was connected to a water splitter catalyst system of considerably larger area than the solar cell. With this design, it was possible to combine a high solar cell efficiently with a low photocurrent density over the electrolyzer (jph = 0.44 mA/cm2), which minimized the overpotential needed for water oxidation. An overall efficiency as high as 18.3% was obtained. 

Photocurrent yield The quantum efficiency of charge photo-generation between the two electrodes of a photovoltaic cell or a photoelectrochemical cell. 

For instance, in a photovoltaic or a photoelectrochemical solar cell, a (small) drop in the electrochemical potential over the active phase is necessary for collecting the electrons [6, 9]. However, it leads to a decrease of the work that an electron can perform in the external circuit. 

In Section 2.4.1, we saw how the photovoltage of a photoelectrochemical cell can be maximised. There is, however, a thermodynamic limit, often called the detailed balance limit, on the photovoltage and consequently of the conversion efficiency. Corresponding theories have been pubhshed (Ross and Hsiao, 1977 Ross and Collins, 1980 Bolton et al, 1980). These theories are apphcable for photovoltaic cells as well as for photoelectrolysis ceUs, and yield a lower limit of a recombination rate which cannot be surpassed. The basic concept of the theory is as foUows. At equilibrium in the dark, the recombination fluxp.dark of radiative transitions across any plane in an ideal ceU is equal to the photon flux emitted by unit surface area of a blackbody, i.e. 

Photoelectrochemical cells are formed by a semiconductor electrode and a suitable counterelectrode immersed into the electrolyte. Three types of photoelectrochemical cells can be distinguished. In photovoltaic cells, the reaction at the counterelectrode is simply the reverse of the photo assisted reaction occurring at the semiconductor electrode so that the cell converts radiant energy into electricity with no change in the composition of the solution or electrodes. 

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