Effect of Cd precursors on luminescence of CdTe quantum dots and their luminescent temperature action
Highly luminescent CdTe quantum dots (QDs) is a typical luminescent material with great application potential. The photoluminescence (PL) and stability of the QDs depended strongly on Cd precursors, ligand (e.g. thioglycolic acid TGA) and preparation conditions. In this paper, CdTe QDs were prepared using Cd precursors with various molar ratios of TGA/Cd at different conditions. The composition of Cd-precursors depend strongly on the molar ratios of TGA/Cd and storage time due to the formation of Cd-TGA clusters which affects strongly the surface states of the QDs. The effect of the preparation conditions of Cd-precursors (e.g. molar ratios of TGA/Cd) on the PL peak wavelength, the full width at half maximum of PL spectra, PL quantum yields (PLQYs), fluorescence lifetime , and stability were tested in detailed. Interestingly, the PLQYs of the QDs prepared using a large molar ratio of TGA/Cd remarkably increased after Cd precursor stored in dark conditions for long time. This confirms that Cd-TGA clusters in the precursors drastically affected the synthesis of the QDs. The mechanism was discussed in detailed. These aqueous CdTe QDs with high PLQYs were obtained using a molar ratio of TGA/Cd of 1.25. In addition, the PL peak position of the QDs was red-shifted with increasing temperature, but is back to the initial value after cooling down to room temperature . Cycle test indicates red-emitting QDs reveal high stability.
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