IPCEs conversion efficiencies

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 ... 

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. 

The performances of the photoelectrochemical cells are strongly dependent on the composition of the electrolyte solution (Fig. 17.22). A maximum conversion efficiency of ca. 80%, in correspondence to the metal-to-ligand charge transfer absorption maximum of N3 was obtained in the presence of 0.25 M LiI/0.025 MI2, whereas with the cobalt-based mediators, the best performances (ca. 50-55% of IPCE) were observed when solutions of Co(DTB)32+/3+ and Co(tTBterpy)22+/3 + were used. In the other investigated cases, Co(phen)32 1 /3 1, Co(tEterpy)22+/3 +, and... 

Figure 3 Incident photocurrent conversion efficiencies (IPCE) observed for the tri-nuclear complex ([fraw-(NC)Ru(py)4(CN)2]Ru(dcbH2))2 + on a 6-(im-thick Ti02 photoanode in the presence of 0.3 M I2 and 0.03 M Lil.

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 ... 

Gregg et at.si) examined photosensitization of perylene pigments (Dye 15-17) on a porous Sn02 thin film instead of Ti02 film as DSC, in view of energy matching with conduction band of semiconductors and LUMO of the sensitizers. When perylene-3,4-dicarboxylic acid-9,10-(5-phenanthroline) carboximide (Dye 15) was used, Jsc of 3.26 mA-cm 2, of 0.45 V, and a photoelectric conversion efficiency of 0.89% were observed under AM 1.5 irradiation. IPCE achieves close to 40% at 460 nm. 

Two devices are prepared. In the case of the device A, the incident photon-to-collected electron conversion efficiency (IPCE) exceeds 80% from 410 to 590 nm, reaching the maximum of 93% at 530 nm. The short-circuit photocurrent density (/sc), open-circuit photovoltage (Voc), and fill factor (FF) of device A with an acetonitrile-based electrolyte under an irradiance of AM 1.5 G full sunlight are 14.33 mA cm-12, 734 mV, and 0.76, respectively, yielding an overall conversion efficiency (jf) of 8.0%. The photovoltaic parameters of device B with a solvent-free ionic liquid electrolyte are 14.06 mA cm 12, 676 mV, 0.74, and 7.0%, respectively. 

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

The incident monochromatic photon-to-current conversion efficiency (IPCE) is plotted as a function of excitation wavelength. The IPCE value in the plateau region is 80% for complex 2, while for complex 25 it is only about 66%. In the red region, the difference is even more pronounced. Thus, at 700 nm the IPCE value is twice as high for the fully protonated complex 2 as compared to the deprotonated complex 25. As a consequence, the short circuit photocurrent is 18-19 mAcrn-2 for complex 2, while it is only about 12-13 mA cm-2 for complex 25. However, there is a trade-off in photovoltage, which is 0.9 V for complex 25, as compared to 0.65 V for complex 2. Nevertheless, this is insufficient to compensate for the current loss. Hence, the... 

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