Efficiency incident photon conversion

FIGURE 8.16 Schematic drawing of experimental setup used for incident photon conversion efficiency measurements. 

Figure 15.44 (a-c) Typical incident photon conversion efficiency (IPCE) plots tor a variety of soiar ceiis. 

Figure 2 shows some representative photocurrent action spectra for the Ti02 electrode alone and in the presnce of the complex tris(4,4 -dicarboxy-2,2 -bipyridine)Ru(II), [Ru(dcbpy)3] and electron donors (bromide or iodide). Plotted are light-to-electrical conversion efficiency for monochromatic radiation as monitored by photocurrent, as a function of wavelength of irradiation. The features of the photocurrent action spectra are similar to the absorption spectrum in homogeneous solution. The incident photon conversion efficiency (IPCE) obtained with the Ru-complex is >70% at the absorption maximum in the visible light region. 

To define the efficiency of solar cells, the following main parameters are used. First, the external quantum efficiency (also called the input photon conversion efficiency tjipce) is defined as the number of generated electrons per incident photon. For a given wavelength X (nm), it is expressed by... 

If an intensifier, such as the 85 mm presented here, is now replacing the screen, a relative gain of the order of x50 is obtained which results in a conversion factor of 1 to 7.5 (1 incident X photon --> 7.5 electrons). This conversion efficiency not only resolves the quantum sink problem but also increases the light level significantly to compensate for the low gamma fluxes obtained from radioactive sources. 

Recently, uniform Filins with high concentrations of Cwl were cast from 1,2-dichlorobenzene solutions containing up to 1 4 weight ratio MEH-PPV [110]. For devices made from these high concentration blends, charge collection efficiencies around //,.=26% (electron/incident photon) and power conversion efficiencies around tjc-2.5% (electrical power out/incident light power) have been realized. 

With the D S SCs containing Hibiscus surattensis extract, the best performances were probably obtained because of the large amount of dye adsorbed on Ti02 (lxl cm2 active surface) in comparison with the other extracts from tropical flowers. Incident photon to current conversion efficiency (IPCE) values of 76% were calculated (2 — 590 nm). Jsc was 5.45 mAcm-2, Voc = 392mV, FF — 54%, and efficiency = 1.14%. Also, the stability of the photovoltaic devices was the best in the case of Hibiscus surattensis, even though it needs to be improved to achieve real long-term stability, especially as far as the sealing quality is concerned. 

The incident monochromatic photon-to-current conversion efficiency (IPCE), also called external quantum efficiency, is defined as the number of electrons generated by light in the external circuit divided by the number of incident photons as a function of excitation wavelength. It is expressed in Equation (7).29 In most cases, the photoaction spectrum overlaps with the absorption spectrum of the sensitizer adsorbed on the semiconductor surface. A high IPCE is a prerequisite for high-power photovoltaic applications, which depends on the sensitizer photon absorption, excited state electron injection, and electron transport to the terminals ... 

Figure 17 Photocurrent action spectra of bare nanocrystalline Ti02 film, and the sensitizers (1), (22), (24), and (57) adsorbed on Ti02 films. The incident photon to current conversion efficiency is plotted as a...

Figure 20 Incident photon to current conversion efficiency of a nanocrystalline Ti02 cell sensitized by dye...

The overall process performance, as measured by photon efficiency (number of incident photon per molecule reacted, like the incident photon to current conversion efficiency, or IPCE, for PV cells), depends on the chain from the light absorption to acceptor/donor reduction/oxidation, and results from the relative kinetic of the recombination processes and interfacial electron transfer [23, 28]. Essentially, control over the rate of carrier crossing the interface, relative to the rates at which carriers recombine, is fundamental in obtaining the control over the efficiency of a photocatalyst. To suppress bulk- and surface-mediated recombination processes an efficient separation mechanism of the photogenerated carrier should be active. 

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. 

Photovoltaic performance of the DSSC is described as follows Figure 8 shows the external spectral response curve of the photocurrent for nanocrystalline Ti02 solar cells sensitized by N3 and black dyes with the I /If redox mediator, where the incident photon-to-current conversion efficiency (IPCE) is represented as a function of wavelength. IPCE is obtained by the following equation ... 

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