Synthesis and characterisation of semiconductor nanoparticle thin films

Due to their unique properties, nanoparticles have been a focus of significantresearch interest for use in various opto-electronic applications, particularlyin the field of solar energy generation. In order to realize a nanoparticlebased solar cell, it is important to be able to create thin films of organisednanoparticles and to be able to control their surface properties.In this work the use of a novel synthesis technique involving reaction at theinterface between two immiscible liquids to synthesise thin films of leadsulfide nanoparticles on the order of ~10 nm in diameter is reported. The useof the liquid-liquid interface allows the synthesis of particles without the useof stabilising ligands, with sizes and morphologies determined by theconditions present at the interface.Variations in the precursor used, solvent height, and precursor concentrationwere explored. Films synthesised at various solvent heights displayed adecrease in particle size with increasing solvent height. This trend was seento vary depending on the lead-containing precursor used.Changes in the precursor concentration resulted in changes in themorphology of the resulting particles as observed with transmission electronmicroscopy (TEM). Preferential growth along certain planes was observedfor particles synthesised with the highest lead precursor concentration.Experiments with precursors with differing organic chain length displayedan increase in particle size with increasing chain length, as well as anincrease in preferential growth observed by X-ray diffraction (XRD).Surface ageing was investigated using X-ray photoelectron spectroscopy(XPS) techniques, which showed that all samples followed a similaroxidation mechanism. Oxidised lead species, attributed to hydrated leadoxide, were determined to be the initial oxidation product, formed within aweek of exposure to air. Sulfoxy species were observed to form over agreater length of time, with sulfate being determined to be the finaloxidation product. An oxidation mechanism is proposed based on XPSanalysis of films exposed to air for up to nine months.