Synthesis, structural and optical properties of water-soluble Mn-doped CdS nanocrystals
Water-soluble Mn-doped CdS nanocrystals were synthesised by an aqueous colloidal synthetic technique. X-ray diffraction identifies that the Mn-doped CdS nanocrystal is a cubic structure without impurity phase. Transmission electron microscopy suggests a narrow size distribution of the nanocrystals with an average particle size of ~3.6~nm. Moreover, UV~vis absorption and photoluminescence (PL) spectra of the nanoparticle were also measured. PL results show that Mn-doped CdS nanocrystals have a distinct Mn2+ related emission well-separated from the trap state emission. Reaction variables such as the 3-Mercaptopropionic acid/Cd (MPA/Cd) ratio, reaction temperature and Mn2+ doped concentration were systematically investigated to evaluate the impact of these variables on particle size and optical property. The results indicate that the 2 mol Mn-doped CdS nanocrystals synthesised at 70 C and the MPA/Cd ratio of 3.5 have the highest PL intensity.
Available from: Volodymyr Chmyrov
- "The red and blue shifts are attributed to the decrease and increase of the band gap (Table 2), respectively. The band gap decreased for these samples of (C)–(E) and increased for these samples of (F)-(G) due to the contribution of Mn as a metal dopant in CdS and the low solid solubility of Mn (<1%) in the CdS nanocrystals    . It means that, below 1%, introduction of Mn could lead to decrease of the band gap but, after 1%, it leads to increase of the band gap because of the MnS phase. "
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ABSTRACT: Colloidal Mn-doped ZnSe/CdS core/shell quantum dots (QDs) are synthesized for the first time and employed as a strategy to boost the power conversion efficiency of quantum dot sensitized solar cells. By using Mn-doping as a band gap engineering tool for core/shell QDs an effective improvement of absorption spectra could be obtained. The mid-states generated by a proper Mn content alleviate carrier separation and enhance the electron injection rate, thus facilitating electron transport to the TiO
substrate. It is demonstrated that a device constructed with 0.25% Mn-doped ZnSe/CdS leads to an enhancement of the electron injection rate and power conversion efficiency by 4 times and 1.3, respectively.
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