Nanocrystalline layer

Impedance spectroscopy and electrochemical dye desorption experiments have been employed [339] to study the electrical characteristics of Ti02 nanocrystalline films in the dark. This study and the others cited above demonstrate how the conductivity changes (as a result of electron injection from the support electrode) can cause the porous/nanocrystalline layer to manifest itself electrically, such that the active region moves away (i.e., outward) from the support as the forward bias voltage is increased. The potential distribution has also been analyzed depending on whether the depletion layer width exceeds or is smaller than the typical dimension of the structural units in the nanocrystalline network [338]. 

During the last 15 years, many investigations have been performed with semiconductor particles or nanocrystals, either dissolved as colloids or used as suspensions in aqueous solutions. Recently films of nanocrystalline layers have also been produced which were used as electrodes in photoelectrochemical systems. Essential results have already been summarized in various reviews [1-9]. All kinds of systems, containing small or large particles have been used in various investigations. In this chapter, the essential properties of semiconductor particles will be described. Small particles, i.e. nanocrystals, are of special interest because of quantum size effects. 

Fig. J0.27 Excitation and electron injection from a dye into Ti02 particles (nanocrystalline layer) large arrows, excitation of the dye by a pump laser thin arrows correspond to an excitation within the conduction band by an additional light beam for probing the injected electrons...

Nanostructures with quantum dots of InP were grown by vapor phase epitaxy from metal-organic compounds with Epiquip VP 50-RP. Self-organized nano-sized InP clusters were grown in Ino.sGao.sP matrix on GaAs <100> substrate [2]. The stmctures contained InP nanocrystalline layer and its effective thickness varied from... 

The thickness of the nanocrystalline layer required to satisfy the last conditions is typically of the order of a few microns depending on the optical cross section of the sensitizer and its concentration in the film as discussed earlier. A simple consideration shows that the electron collection efficiency is related to the electron transport (fx) and recombination time (tr) or the respective electron transfer and recombination resistances (R and/ ct) by the equation [55] ... 

Bueno, P.R., E.R. Leite, T.R. Giraldi, L.O.S. Bulhoes, and E. Longo, Nanostructured Li ion insertion electrodes. 2. Jin dioxide nanocrystalline layers and discussion on Nanoscale Effect. Journal of Physical Chemistry B, 2003. 107 pp. 8878-8883... 

Cross-section TEM images and selected area electron diffraction of the carbonized layer before and after wet oxidation at 800 °C are presented in Fig. 2. Well ordered silicon crystalline structure and porous morphology can be seen before oxidation. After oxidation a complete amorphization of the nanocrystalline layer and reduction of porosity took place. 

In turn, Yang et al. demonstrated DC EL from a hybrid CdS Mn/ZnS and conjugated polymer [32]. EL devices were prepared from multilayer structures of ITO/PEDOT PSS/conjugated polymer/CdS Mn/ZnS NCs/Al, using two different conjugated polymers (PVK and PPV). Nanocrystal hybrid EL devices with PVK and PPV are characterized by orange and green EL emission, respectively, which means that electron-hole recombination is confined to the CdS Mn/ZnS nanocrystalline layer in PVK-based devices, but occurs in the PPV layer in PPV-based devices [32]. 

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