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Title: Photoelectrochemistry of nanostructured semiconductors
Author: Bradley, Kieren Adam
ISNI:       0000 0004 5914 6055
Awarding Body: University of Bristol
Current Institution: University of Bristol
Date of Award: 2015
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Semiconductors are vital components in the challenge of harvesting solar power to provide sufficient carbon neutral energy for a growing global population. A trend in semiconductor devices is to nanostructure some of the layers in order to obtain improvements in optical and electrical properties. This work focusses on two materials that have been gaining academic and commercial interest over a number of years. Zinc oxide (ZnO) is a wide bandgap semiconductor that can be grown via a number of physical and chemical deposition methods; the work on ZnO builds upon research on a chemical growth route which can create well aligned hexagonal rods with diameters from ~20 nm to Illm, with lengths of hundreds of nanometres to tens of microns. Changes in the growth solution led to either aligned or disordered rods, but the irreproducibility of the technique is evident. The second material studied is indium gallium nitride (InxGa1-xN), a semiconductor which can have its optoelectronic properties tuned by changing the ratio of In to Ga. Tuneable bandgaps are desirable for absorbing the optimum fraction of solar energy. Photoelectrochemistry is used to probe the optoelectronic characteristics of the semiconductors and theoretical models are used to simulate the combination of the optics and electronics in nanostructured electrodes, with waveguiding effects being shown to alter the expected efficiency of photoelectrochemical reactions in nanorods. A model based on the semiconductor continuity equation and Shockley-Read-Hall recombination is developed to describe the time dependent photoelectrochemical current of semiconductors with mid-band defect states, as functions of applied potential and illumination intensity. From the model a novel technique is provided to calculate the position and density of the defect states; the technique is successfully demonstrated on ZnO nanorods for the first time and evaluated for its effectiveness .
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available