| Due to the narrow photoluminescence spectra, high photoluminescence quantum yield, good stability and biocompatibility, and also with different sizes can be excited at single wavelength, there is a broad application of semiconductor quantum dots(QDs) in the filed of biolables and semiconductor photoelectric device. For many drawbacks of the organometallic route such as toxic, expensive, pyrophoric, and even explosive, in this thesis, series of quantum dots in aqueous solution was synthesized by the using of thiols as the capping agent. This method is simple and controllable, and good optical properties was obtained by the as-prepared quantum dots. By the following, water soluble CdSe QDs was applied to the TiO2 electrode based solar cells. The achieved results are stated as following:(1) The synthesis of highly stable water soluble CdTe using dithiol as the capping agent and highly luminescent CdS QDs using bio-stablizer as the capping agent.Highly luminescent CdTe nanocrystals was synthesized by hydrothermal method using dihydrolipoic acid (DHLA) as capping reagent. The influence of various experimental parameters, including pH value, Te-to-Cd ratio, as well as Cd-to-ligand ratio on the growth rate and optical properties of the obtained CdTe nanocrystals have been systematically investigated, and the stability of the DHLA capped CdTe nanocrystals was researched by contrasting with TGA and MPA capped CdTe nanocrystals. The maximum quantum yield of DHLA capped CdTe QDs was 42%, FWHM=?50 nm. And the DHLA capped nanoparticle showed better stability than the nanoparticles when TGA or MPA as the capping agent. The mechanism for the resulting high-quality optical properties and the goodish stability of the resulting CdTe nanocrystals is also elucidated.Highly luminescent CdS nanocrystals (maximum quantum yield of 36%) by the reaction of Cd2+ and thiourea with glutathione (GSH) as the capping reagent. The influence of various experimental variables, including pH value, S-to-Cd ratio, as well as Cd-to-ligand ratio on the growth rate and optical properties of the obtained CdS nanocrystals have been systematically investigated. Experimental results indicate that the pH value and Cd-to-ligand molar ratio play the crucial role in determining luminescent properties of the obtained CdS nanocrystals. Furthermore, the photoluminescence intensity can be enhanced significantly when the nanocrystals sample is illuminated by room light. The mechanism for the resulting high-quality optical properties of the resulting CdS nanocrystals is also elucidated.(2) Depositing a ZnxCd1-xS shell around CdSe core nanocrystals via a noninjection approach in aqueous mediaThe deposition of the ZnxCd1-xS shell around CdSe cores was carried out at 90?in a reaction flask uses CdCl2, Zn(OAc)2 and thiourea as Cd, Zn, and S sourceconsisting of the precursor compounds, together with CdSe nanocrystal cores and the capping reagent glutathione. The optical features and structure of the obtained CdSe/ZnxCd1-xS core/shell nanocrystals have been characterized by UV-vis, PL spectroscopy, TEM and XRD. The influences of various experimental variables, including Cd-to-Zn ratio, amounts of ligand and thiourea as well as pH value on the growth rate and luminescent properties of the obtained core/shell nanocrystals have been systematically investigated. Through the optimization of experimental variables, the obtained water soluble core/shell nanocrystals possess highest emission efficiency of 35% and spectral width less than 30 nm.(3) The synthesis of highly luminescent UV-blue-emitting ZnSe/ZnS core/shell nanocrystals and ZnSe/ZnS based transition metal ions doped nanocrystalsHigh-quality water-dispersible ZnSe/ZnS core/shell nanocrystals have been prepared in aqueous media carried out at 90?. The optical features and structure of the obtained ZnSe/ZnS core/shell nanocrystals have been characterized by UV-vis, PL spectroscopy, TEM, XRD and EDS. The influences of various experimental variables, including amounts of ligand and thiourea as well as pH value on the growth rate and luminescent properties of the obtained core/shell nanocrystals have been systematically investigated. The PL QY of the as-prepared water-soluble ZnSe/ZnS core/shell QDs is up to 65%. In comparision with the plain ZnSe core nanocrystals, both the PL emission efficiency and the stability against UV irradiation and chemical oxidation of the ZnSe/ZnS core/shell nanostructure have been greatly improved.High-quality water-dispersible Mn doped ZnSe core/ZnS shell (Mn:ZnSe/ZnS) nanocrystals have been synthesized directly in aqueous media. The quantum yields of the dopant Mn photoluminescence emission in the as-prepared water-soluble Mn:ZnSe/ZnS core/shell nanocrystals can be up to 35%. The optical features and structure of the obtained Mn:ZnSe/ZnS core/shell nanocrystals have been characterized by UV-vis, PL spectroscopy, TEM, XRD and ICP elementary analysis. The influences of various experimental variables, including the Mn concentration, the Se/Zn molar ratio as well as the kind of capping ligand used in the core production and shell deposition process, on the luminescent properties of the obtained Mn:ZnSe/ZnS nanocrystals have been systematically investigated. (4) The application of water-soluble CdSe QDs in solar cellsWater-soluble CdSe QDs was employed as sensitizers to the TiO2 electrode based solar cells. The influence of the size and the absorption time of the water-soluble CdSe QDs has been investigated, the effect of the water-soluble CdSe QDs was contrasted with the corresponding of oil-soluble CdSe QDs. The absorption amount of water-soluble CdSe QDs could improve by a factor of 2.5-3 with respect to oil-soluble CdSe QDs. The photo-current and the photo-current conversion efficiency of the water-soluble CdSe QDs based solar cells could achieve 11.08 mA/cm2?1.75% compared with 6.27 mA/cm2?0.85% of the oil-soluble CdSe QDs solar cells. And the photo-current conversion efficiency could reach 2.58% by Cu2S as the counter-electrode instead of Pt. |
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