Monolayer action spectrum

A typical photocurrent action spectrum is illustrated in Figure 10 together with the excitation spectrum of the ZnTOAPP monolayer. The good correspondence between the two curves indicates that the dye is, in fact, the source of the photocurrents observed. 

Figure 10. Action spectrum of a monolayer of ZnTOAPP (ZnTOAPP.SA octa-decane, 1 4 3) directly on a Sn02 OTE 0.1 M KCl, pH 7.0, electrode potential is...

Light excitation of a Chla membrane deposited on Pt resulted in a weak photocurrent with the Pt/Chla behaving as a cathode. The photocurrent action spectrum resembled the Chla absorption spectrum which ruled out a direct photoemission process. The direction of the photocurrent was rationalized by invoking a p-type conductivity in the Chla films. Bolton and co-workers explored related monolayer assemblies with spatially organized quinones to increase efficiencies ]41]. In a more promising system, Chla monolayers deposited on A1 contacts with uboquinone ac-... 

The mixed SAM under discussion here has been designed to overcome this limitation and to increase the photocurrent efficiency in the visible part of the spectrum. The strong overlap of the emission spectrum of BoDy with the absorption of Fc-P-C6o in the 500 nm region is anticipated to facilitate efficient energy transfer between the two species. The photochemical action spectra of the mixed monolayer show contributions from both BoDy and Fc-P-C6o- The overall behavior of the assembly is therefore in agreement with the scheme shown in Figure 5.34. At 510 nm, a much increased quantum yield for photocurrent production of 50 % is obtained. This study shows that photocurrents can be created at metal electrodes. Relatively high photocurrent efficiencies are obtained however, the fact that flat surfaces are used rather than the nanocrystalline approach taken for semiconductor substrates (see Chapter 6) means that the incident photocurrent efficiency (IPCE) values are... 

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