Charge transport nanostructures

In sum, then, although fascinating reports of conductivity in DNA structures have been published, and some general structure/function motifs have become clear, difficulties with reproducibility of experimental data and with appropriate interfaces between nanoscale DNA structures and macroscopic electrodes have limited the accuracy with which DNA charge transport can be measured, and the depth in which it can be understood. This remains an active area, and (especially given DNA s very powerful presence as the synthetic component of nanostructures) it is one that will almost certainly be more clearly elucidated in the near future. 

It would be appropriate now to discuss charge transport in the different layers of the cell. However, experimental data on this topic have remained very scarce. Most work has focused on electronic transport in nanostructured films used for substrates, particularly TiOi and ZnO. 

Figure 7.8 Centre Current density-voltage characteristics of hybrid poly-3-hexylthiophene ZnO devices with different morphology. The device based on a layer of vertically oriented ZnO nanorods outperforms the device based on ZnO nanoparticles of similar diameter, while both nanostructured films outperform the bilayer. Left Scanning electron microscope image of ZnO nanoparticle film. Right SEM image (side view) of ZnO nanorod film. The superior performance of the ZnO nanorod-based film is attributed to the paths for charge transport, which are directed towards the electrodes (Ravirajan et al, 2006).

In this chapter we report on properties of nanometer-sized semiconductor particles in solution and in thin films and thereby concentrate on the photochemical, photophysical, and photoelectrochemical behavior of these particles. We shall, very briefly, describe the energetic levels in semiconductors and the size quantization effect. The bottleneck in small-particle research is the preparation of well-defined samples. As many preparative aspects are already reviewed in several actual assays, we present here only the preparative highlights of the last two years. In Section IV we describe the fluorescence properties of the particles. We report on different models for the description of the very complex fluorescence mechanism and we show how fluorescence can be utilized as a tool to learn about surface chemistry. Moreover, we present complex nanostructures consisting of either linked particles or multiple shells of different nanosized materials. The other large paragraph describes experiments with particles that are deposited on conductive substrates. We show how the combination of photoelectrochemistry and optical spectroscopy provides important information on the electronic levels as well as on charge transport properties in quantized particle films. We report on efficient charge separation processes in nanostructured films and discuss the results with respect to possible applications as new materials for optoelectronics and photovoltaics. 

Bouchet, R., Phan, T. N. T, Beaudoin, E., Devaux, D., Davidson, R, Bertin, D., et al. (2014). Charge transport in nanostructured PS-PEO-PS triblock copolymer electrolytes. Macromolecules. 47f81.2659-2665. 

Various kinds of conducting polymers can work as coimter electrode in DSSC. Poly(3,4-ethylenedioxythiophene) (PEDOT), polypyrrole (PPy), PANI are most investigated polymer materials. With the development of nanomaterial, the nanostructure has been introduced into previously mentioned polymers. These polymers are readily deposited by either chemical or electrochemical polymerization process. And they are readily modified into aligned nanostructure that might enhance charge transport and surface area simultaneously (Sun et al., 2015a). 

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