Photoexcitation and Carrier Collection Steady State Behavior

Photoexcitation and Carrier Collection Steady State Behavior 

as is the case with Ti02 nanocrystalline films, the holes are rapidly scavenged 

It is important to reiterate that the charge separation in a nanocrystalline semiconductor-electrolyte interface does not depend on a built-in electric field at the junction as in the single-crystal 

Photocurrent losses have been recorded for electrolytes dosed with electron acceptors such as O2 and iodine [226]. Nanocrystalline Ti02 electrodes with thicknesses ranging from 2 pm to 38 pm were included in this study. In the presence of these electron-capture agents, electron collection (i.e. photocurrent) at the rear contact was seriously compromised. On the other hand, as high as 10% of the photons were converted to current for a 38 pm thick film in a N2-purged solution [226]. 

The result was obtained with front-side illumination geometry. As one would intuitively expect, carrier collection is most efficient close to the rear contact. Indeed, marked differences have been observed for photoaction spectra with the two irradiation (i.e. through the electrolyte side vs. through the transparent rear contact) geometries for Ti02, CdS, and CdSe nanocrystalline films [227, 228]. Obviously, the relative magnitudes of the excitation wavelength and the film thickness critically enter into this variant behavior. 

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Photoexcitation and Carrier Collection Steady State Behavior. 38... 

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