| Semiconductor nanomaterials, especially semiconductor nanocrystals of Ⅱ-Ⅵ series, Ⅲ-Ⅴ series and Ⅳ-Ⅵ series have been extensively used in the fields of optical, electric and superconductivie instruments. The optical, electric and mechanical properties are directly influenced by size, morphology and energy structure of the semiconductor nanaocrystals, so it is very important to synthesize the high-quality semiconductor nanocrystals and control their size and shape. As the quantum yield of quantum dots composed by Ⅱ-Ⅵ series elements are relative high, their fluorescence spectra cover the whole visible range even extend to the near infrared range, and the water solubility of quantum dots synthesized in water is very well, quantum dots of this type could be used in biological label, biological image and biological probe. The bandgaps of the semiconductor nanocrystals of Ⅳ-Ⅵ series are very narrow, especially for SnS. SnS has a bandgap of1.3eV, which matches well with the near infrared and infrared ranges of solar spectrum. If SnS is used as the absorbing material, it could use the low energy of light. Meanwhile, SnS has high light throughput efficiency, and the elements of Sn and S are rich and non-toxic, so SnS is a kind of ideal material to prepare the photoconduction device, detector of near infrared and photovoltaic cells. The main content of this thesis is the research in synthesizing CdSexTe1-x/ZnS quantum dots and SnS nanocrystals and investigating their optoelectrical properties.1. CdSexTe1-x/ZnS quantum dots with a Type-I core/shell structure were synthesized in aqueous phase under refluxing. The Type-I structure not only increases the quantum yield of inner core quantum dots, but also lowers the toxicity of inner quantum dots. In this section, high efficient CdSexTe1-x alloy quantum dots composed by CdSe and CdTe were used as the core, and low toxic ZnS was used as the shell. The research results show that the fluorescence emission wavelength of this core quantum dots could be adjusted not only by the size but the ratio of composing elements. In this section, the influence factors about refluxing time, pH value and mole ratio of Se to Te on the fluorescence emission spectra of CdSexTe1-x quantum dots, and the influence of refluxing time, mole ratio of Se to Te, shell number of the capped ZnS and aging time on the fluorescence emission spectra of CdSexTe1-x/ZnS quantum dots have been investigated, respectively. The experiments results demonstrate that the fluorescence emission intensity of CdSexTe1-x/ZnS quantum dots that was synthesized at a pH value of about9, a mole ratio (Se to Te) of1:2, and two-layer covered ZnS shell is highest. In addition, the quantum yield increased noticeably after the CdSexTe1-x/ZnS quantum dots were aged.2. In the second part, SnS nanocrystals with different shapes and sizes were synthesized at lower temperature of180℃by using the hot injection method. In this method, SnO was used as Sn(Ⅱ) source, octadecene was used as the solvent, and oleic aicd and oleylamine were used as ligand agents. The influence of volume ratio of oleic acid to oleylamine, synthesis temperature, the mole ratio and concentration of Sn(Ⅱ) to S on the morphology and crystallinity of SnS nanocrystals were studied. The results show that the crystalline phases of SnS nanocrystals synthesized in different conditions are the same mixed phases of cubic (major phase) and orthorhombic (minor phase). Moreover, the photocurrent and cyclic voltammetry properties of calcined SnS films were investigated. The results show that the average photocurrent is stable and reaches to3.8nA/cm2. The research of SnS in this section provides the useful experimental data for the study of solar cells. |
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