Incident photon to current conversion efficiency

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. 

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 ... 

Bach et al. have successfully introduced the concept of a solid p-type semiconductor (heterojunction), with the amorphous organic hole-transport material 2,2, 7,7 -tetrakis (, V, V-di-/ -methoxyphcnyl-aminc)9,9 -spirobifluorenc [96]. This hole-conducting material allows the regeneration of the sensitizers after electron injection due to its hole-transport properties. Nevertheless, the incident photon-to-current conversion efficiencies using complex 22 as a charge-transfer sensitizer... 

The photoelectrochemical properties of different semiconductor materials have been widely reported, for single crystal, polycrystalline, as well as for nanostructured materials. In the literature various methods for measuring the efficiency are found. The most common is the JPCE (incident photon-to-current conversion efficiency) or quantum efficiency, which is defined as... 

IPCE Incident-photon-to-current-conversion efficiency... 

Photosystem I. The quantity of photocurrent varied with the type and age of electrode as is evident from the data in Table I. Some freshly made Ti02 electrodes generated low currents even in the absence of PSI. The incident photon to current conversion efficiency, defined as the number of electrons injected by the excited sensitizer (and recorded as photocurrent) divided by the number of incident photons, was calculated from the equation ... 

Finally, we carried out measurements on complete functional devices. We measured the incident photon-to-current conversion efficiency (IPCE) spectra for devices sensitized with AR25 using as electrolyte a solution containing the redox couple iodine/iodide (see Experimental Section). Figure 4 illustrates the IPCE spectra for an AR25/DSSC. 

The incident photon to current conversion efficiency (IPCE) sometimes referred to also as external quantum efficiency (EQE) corresponds to the number of electrons measured as photocurrent in the external circuit divided by the monochromatic photon flux that strikes the cell. The following product expresses this key parameter ... 

Fig. 15 Conversion of light to electric current by dye-sensitized solar cells. The incident photon to current conversion efficiency is plotted as a function of the excitation wavelength. Left single crystal anatase cut in the (001) plane. Right nanocrystaUine anatase film. Pictures of the two electrodes used as current collectors are also presented. The electrolyte consisted of a solution of 0.3 M Lil and 0.03 M fr in acetonitrile...

Fig. 5 Photocurrent vs potential plot recorded for a ca. 45 pm thick nanoparticulate Ti02 film, immersed in a 0.1 M HCIO4/0.1 M HCOOH solution and irradiated with a 300-nm monochromatic light (700 pW cm ) from the side of the film/solution boundary. On the left axis is represented the corresponding incident photon-to-current conversion efficiency (IPCE). In the insert is represented schematically (marked in grey ) the illuminated part of the Ti02 film where the electron injection takes place. (Reproduced with permission from [12])...

Ru(phen)2Cl] is more efficient than Zn-35 and a 13% IPCE has been measured at the Soret band. Also, much lower efficiencies have been obtained for the free-base derivatives and assigned to the lack of a coordination point to the nanocrystalline Ti02 surface. Even the solvent used for the adsorption of the sensitizer has been found to influence the IPCE (Incident Photon to Current Conversion Efficiency = 1,250(/sc/ ). where Jsc is the short-circuit photocurrent density, X the wavelength, and (f) the photon flux). 

When trying to identify performance-limiting factors in PEC photoelectrodes, the quantum efficiency as a function of wavelength is a particularly useful parameter. The definition of the external quantum efficiency is the fraction of the incident photons that is converted to electrons that can be measured by the outer circuit. This is the IPCE incident photon-to-current conversion efficiency), which is given by... 

Successive cycles of thiophene terminal bromination and Suzuki-type coupling reactions with 3-hexylthiophene-2-boronic ester gave intermediate ter- and quaterthiophenes. Formylation of these intermediates and final condensation with cyanoacetic acid in basic medium afforded corresponding oligothiophenes in 70-90% yields. UV-Vis absorption spectra of 2.82 (n = 1, 2) showed maxima at 463 and 473 nm, respectively. Fabrication of DSSCs based on 2.82 (n = 1, 2) showed a high incident photon-to-current conversion efficiency (IPCE) of 70 % in the range 400-650 nm and good maximum power conversion efficiencies of 7.7 and 5.6% under AM 1.5 illumination. 

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