Photoelectrolysis conversion efficiency

Principal solar water-sphtting models had predicted similar dual band gap photoelectrolysis efficiencies of only 16% and 10-18% [3, 28], respectively, whereas recently dual band gap systems were calculated to be capable of attaining over 30% solar photoelectrolysis conversion efficiency [14]. The physics of the earlier models were superb, but their analysis was influenced by dated technology, and underestimated the experimental jjphoto attained by contemporary devices or underestimated the high experimental values of JJelectrolysis which Can be... 

Fig. 3.20 The ideal limiting solar conversion efficiency for single bandgap devices. The dotted line shows efficiency of photoelectrolysis cells at different values of Eioss in relation (3.6.8) [102].

Though equation (3.6.5) is more useful for analyzing the performance of photoelectrolysis cells, for practical purposes the photoconversion efficiency (solar conversion efficiency if sunlight is used) is calculated hy modifying (3.6.5) in the form... 

A very useful parameter for evaluating the performance of a photoelectrolysis cell is the incident photon to current conversion efficiency (IPCE). This is a measure of the effectiveness in converting photons incident on the cell to photocurrent flowing between the working and counter electrodes. IPCE is also called the external quantum efficiency. 

Hanna MC, Nozik AJ (2006) Solar conversion efficiency of photovoltaic and photoelectrolysis cells with carrier multiplication absorbers. J Appl Phys 100 074510 (8 pages)... 

This chapter considers the fabrication of oxide semiconductor photoanode materials possessing tubular-form geometries and their application to water photoelectrolysis due to their demonstrated excellent photo-conversion efficiencies particular emphasis is given in this chapter to highly-ordered Ti02 nanotube arrays made by anodic oxidation of titanium in fluoride based electrolytes. Since photoconversion efficiencies are intricately tied to surface area and architectural features, the ability to fabricate nanotube arrays of different pore size, length, wall thickness, and composition are considered, with fabrication and crystallization variables discussed in relationship to a nanotube-array growth model. 

As for photoelectrolysis of water at p-type semiconductors, Heller and co-workers studies of InP electrodes should be mentioned [77, 81]. A solar to chemical conversion efficiency as high as 12% was reported for this system [77, 81], with relatively low stability. 

Fig. 9. Energy conversion efficiency of solar driven water splitting to generate H2 as a function of temperature for AMI. 5 insolation, with the system minimum bandgap determined at JOH20 = 1 bar.3 The maximum photoelectrolysis efficiency is shown for various indicated values...

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. 

If energy is to be stored in a chemical fuel, for instance by prodncing H2 via the photoelectrolysis of H2O, further energy losses due to overpotentials have to be enconntered. The two overpotentials, /ox and are defined as the difference between the qnasi-Fermi level and the corresponding redox potential. Using eq. 2.72, the conversion efficiency for the prodnction of a chemical fnel is then given as... 

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