Solar photocurrent

Fig. 3.25 (a) The solar photocurrent spectrum of a titania nanotube array obtained using data from Fig. 3.19 and Fig. 3.24. (b) The total solar photocurrent obtained by integrated the photocurrent of (a). 

Here, /solar is the total solar photocurrent in A/m and 0(2) is the photon flux of srmlight in photons/m /s. The photon flux can be calculated from tabulated solar... 

Designing tandem cells is complex. For example, each cell must transmit efficiently the insufficiently energetic photons so that the contacts on the backs of the upper cells are transparent to these photons and therefore caimot be made of the usual bulk metal layers. Unless the cells in a stack can be fabricated monolithically, ie, together on the same substrate, different external load circuits must be provided for each cell. The thicknesses and band gaps of individual cells in the stack must be adjusted so that the photocurrents in all cells are equal. Such an optimal adjustment is especially difficult because the power in different parts of the solar spectmm varies under ambient conditions. Despite these difficulties, there is potential for improvement in cell conversion efficiency from tandem cells. 

Preliminary measurements with space-resolved PMC techniques have shown that PMC images can be obtained from nanostructured dye sensitization cells. They showed a chaotic distribution of PMC intensities that indicate that local inhomogeneities in the preparation of the nanostructured layer affect photoinduced electron injection. A comparison of photocurrent maps taken at different electrode potentials with corresponding PMC maps promises new insight into the function of this unconventional solar cell type. 

Electrolyte contacts have been used to characterize as-deposited and annealed CdS/CdTe solar cell structures by photocurrent spectroscopy and electrolyte elec-troabsorbance/electroreflectance measurements (EEA/EER) [267-269]. 

Duffy NW, Peter LM, Wang RL, Lane DW, Rogers KD (2000) Electrodeposition and characterisation of CdTe films for solar ceU applications. Electrochim Acta 45 3355-3365 Duffy NW, Peter LM, Wang RL (2002) Characterisation of CdS/CdTe heterojunctions by photocurrent spectroscopy and electrolyte electroreflectance/absorbance spectroscopy (EEA/EER). J Electroanal Chem 532 207-214 (see also references therein). 

Table 1. Photovoltage Up, photocurrent ip fill factor FF and efficiency p of regenerative electrochemical solar cells... 

Despite the potential impact of novel photosynthetic routes based on these developments, the most ambitious application remains in the conversion of solar energy into electricity. Dvorak et al. showed that photocurrent as well as photopotential response can be developed across liquid-liquid junctions during photoinduced ET reactions [157,158]. The first analysis of the output power of a porphyrin-sensitized water-DCE interface has been recently reported [87]. Characteristic photocurrent-photovoltage curves for this junction connected in series to an external load are displayed in Fig. 22. It should be mentioned that negligible photoresponses are observed when only the platinum counterelectrodes are illuminated. Considering irradiation AM 1, solar energy conversions from 0.01 to 0.1% have been estimated, with fill factors around 0.4. The low conversion... 

Wang, X. F., Y. Koyama, H. Nagae, Y. Yamano, M. Ito, and Y. Wada. 2006. Photocurrents of solar cells sensitized by aggregate-forming polyenes Enhancement due to suppression of singlet-triplet annihilation by lowering of dye concentration or light intensity. Chem. Phys. Lett. 420 309-315. 

The overall conversion efficiency (rj) of the dye-sensitized solar cell is determined by the photocurrent density (7ph) measured at short circuit, Voc, the fill factor (fif) of the cell, and the intensity of the incident light (7S) as shown in Equation (9). 

The photocurrent action spectra of these complexes show broad features covering a large part of visible spectrum, and display a maximum at around 550 nm, where the incident monochromatic IPCE exceeds 85%. These hydrophobic complexes show excellent stability towards water-induced desorption when used as CT photosensitizers in nanocrystalline Ti02-based solar cells.62... 

In order to obtain high conversion efficiencies, optimization of the short-circuit photocurrent and open-circuit potential of the solar cell are essential. The conduction band of the Ti02 is known to have... 

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