| Summary: | 碩士 === 國立清華大學 === 化學工程學系 === 100 === We synthesized the lead sulfide quantum dot by a simple method and by controlling the content of dispersant (2wt%); PVA (polyvinyl alcohol) and the feeding rate of the precursor (0.4ml/min) we could control the exact size quantum dot. Lead sulfide quantum dot was characterized by transmission electron microscopy (TEM), X-ray electron diffraction (XRD) and Ultra violet-visible-near infrared spectroscopy (UV-Vis-NIR). Results show that lead sulfide quantum dot with an average diameter 4.57 nm and the narrow size distributions was obtained. Its standard deviation is 1.2nm. Furthermore, there are above 80.8% (N %) QDs have the higher conduction band than anode material (TiO2). Because aqueous phase QDs have the higher surface tension than organic phase, the QDs is hard to diffusion into the porous of TiO2. Besides, the aqueous phase dispersant (PVA) absorption on the surface of QDs would inhibit the electron transport. Therefore, we desire a phase transfer approach to solve these problems. We prepare the stable dispersion of lead sulfide (PbS) quantum dot in organic solvent by phase transfer. From the FTIR and absorption spectrum, after phase transfer the –OH group signal from the PVA is decrease and the molar absorptivity become 2.2 times. We study the content of the pentanol that affects the phase transfer efficiency, and after optimizing pentanol content the phase transfer efficiency is 90.6%. Afterward we apply the QDs in the quantum dot-sensitized solar cells the efficiency is 0.26%.
On the other hand, we synthesized one dimensional core-shell structure, zinc oxide was coated on the silver nanowire, where the diameter of Ag nanowire was 100 nm and the thickness of zinc oxide coating was 10nm. The polymer PVP (Polyvinylpyrrolidone) assisted the ionic zinc species absorption on surface of Ag. The Ag nanowire provided the high speed channel for electron passing through the anode to arrive to the external circuit. We change the ratio between the Zn2+ and Ag nanowire in the hydrothermal reaction. Observed the morphology of core-shell structure and found the layer-plus-island group.
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