Photocurrent action spectra

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... 

Figure 12 Photocurrent action spectra of nanocrystalline Ti02 films sensitized by fe(3,4-dicarboxypyridine) Ru11 (1,4,8,11,15,18,22,25-octamethyl-phthalocyanin) (54). The incident photon to current conversion...

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...

Fig. 7.5 Photocurrent action spectra of (a) Ti02 (thickness = 1 m, electrolyte = 0.01 M NaOH), (b) CdSe, and (c) Ti02-CdSe (thickness = 15 nm, electrolyte = 0.5 M [Fe(CN)6] and 0.1 mM [Fe(CN)6] , pH =12) thin film electrodes. Reprinted with permission from Ref. [51].

The performance of the three sensitizers 22,8 and 56, which contain different degrees of protonation were studied on nanocrystalline TiO2 electrodes [80]. Figure 13 show the photocurrent action spectra obtained with a monolayer of these complexes coated on TiO2 films. 

Fig. 35 Transient photocurrent action spectra for holes and electrons in PTS (p-toluenesulphonate)-polydiacetylene single crystals. The dashed curve in the spectra for holes corresponds to the absorption spectrum of the polymer dispersed in KBr. (After Chance et al.,...

When holding the composite films at 0 V (vs. Ag/AgCl) under illumination (A < 450 nm), an anodic photocurrent was observed in the presence of a triethanolamine donor whose relative efficiency was dependent on the excitation wavelength. There was good agreement between the absorption spectra of a dispersion of CdS nanoparticles and the photocurrent action spectra. This indicated that the CdS particles maintained their integrity in the multilayer without any problems of aggregation. 

Fig. 4.3. Photocurrent action spectra for WO3 electrode sensitized by Dye II in monomeric form...

Fig. 4.4. Photocurrent action spectra for W03 electrode sensitized by thiacarbocyanine dye in monomeric form (dashed line) aggregated by coprecipitation with PD III (solid line). Electrode potential +0.6 V. Electrolyte 0.25 M Na2S04.

Fig. 4.6. Photocurrent action spectra (curves 1, 2) and absorption spectrum (curve 3) of aggregated Dye III embedded in the nanostructurated TiOz film electrolyte 0.25 M Na2S04 light intensity 10 4 W cm 2 electrode potential +0.3 V (curve 1), -0.2 V (curve 2). Absorption spectrum of dyed Ti02 colloid (50 mmol/1 of titania + 1 mmol/1 of Dye III) used for fabrication of volume-sensitized nanostructurated Ti02 electrode. Dye III exhibits J-aggregation upon adsorption at Ti02 particles.

Fig. 4.7. Photocurrent action spectra for W03 electrode sensitized by Dye I (dashed line) and Dye I coprecipitated with PD IV (solid line). Spectral distribution of the relative variation in photocurrent Aiph/iph = 1 - iPh(t)/iPh(0), where iph(0) and iph(t) are measured before and after illumination of the positively-biased Dye I PD IV-sensitized W03 electrode (E = 0.6 V) at 550 nm for 10 min. Electrolyte 0.25 M Na2S04.

Fig. 4.15. Photocurrent action spectra for ITO/WC Dye IV heterojunction under illumination through the transparent back contact (curves 1, 2, 5, 7) through the solution (curves 3,4, 6, 8). Dye IV was aggregated by heating at 120°C (curves 1, 3, 7, 8). Electrolyte 0.25 M Na2SC>4.

Porphyrin 37a and 37b have also been employed as sensitizer for a TiC>2 nanotube electrode. For comparison purpose, asymmetrical porphyrin sensitizer with two carboxylic acid groups (38, 39) and 28 have also been tested under identical conditions. The DSSC fabricated from these sensitized Ti02 nanotube presents enhanced charge-collection efficiency respect to the nanoporous Ti02 film built from Ti02 nanoparticles. All the tested five porphyrin sensitizers exhibited efficient sensitization to Ti02 nanotube as revealed by the photocurrent action spectra. 

Photoelectrochemical measurements also provide an approach to the determination of electrophysical characteristics of diamond. In addition to the threshold energies of electron phototransitions, determined by the analysis of the photocurrent action spectra (Section 7), the diffusion length of minority carriers in polycrystalline diamond films was estimated (at 2 to 4 pm) by comparing light absorption spectra and open-circuit potential spectra [171],... 

Fig. 5.1. (a) Photocurrent action spectra for ITO/PBI(20 nm)/M3EH-PPV(35 nm)/Au (circles) and ITO/M3EH-PPV(44 nm)/PBI(24 nm)/Au (squares) on the left-hand side axis. The absorption spectra of M3EH-PPV (dashed line) and PBI (dotted line) are shown on the right-hand side axis for comparison, (b) Absorption spectra of M3EH-PPV (left curve), PBI (middle curve) and MgPc (right curve) [128]. 

Valerian and Nespurek (1993) determined values of the electron range (mobility-lifetime product) of vapor-deposited a-H2Pc from measurements of the photocurrent action spectra. The values were about 6 x 10-12 cm2/V, considerably lower than 10-9 cm2/V reported earlier by Popovic and Sharp (1977) for /J-H2Pc. For further discussions of photoconductivity in n-type phthalocyanies, see Schlettwein et al. (1994, 1994a), Meyer et al. (1995), and Karmann et al. (1996,1997). 

An intriguing feature of the VSe2 electrodes sensitized with the thiapentaearbo-cyanine was that the photocurrent action spectra were a function of the bias potential applied to the electrode. For example, the maximum conversion efficiency at -0.4 V vs. Ag/AgCl was 1100 nm but shifted to 1080 nm at -1-0.05 V. The origin of these spectral shifts was attributed to sensitizer aggregates formed on the surface that have different conversion efficiencies [92]. 

Experiments using a two-layer heterostructure in which the photocurrent action spectra are observed both for front and rear (symbatic and antibatic) illumination of the interfaee between a photosensitizer and a hole transport layer have shown that the surface enhaneement of bound pair generation is due to a layer typieally 300-500 nm thiek [13]. Within this distance of the interface, excitons generated by the optieal absorption may diffuse toward the interface and initiate bound pair generation. The importanee of these excitons for a specific photoreceptor can be iden-... 

Pettersson L. A. A., Roman L. S. and Inganas O. (1999), Modeling photocurrent action spectra of photovoltaic devices based on organic thin films , J. Appl. Phys. 86, 487 96. 

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