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Cu-doped quantum dots( QDs) were used as color converting materials for preparing efficient white light-emitting diodes( LEDs). The Cu-doped QDs synthesized by chemical method showed composition-tunable emission from green to deep red and large Stokes shifts. By using the combination of green light-emitting Zn In S∶ Cu QDs and red emitting Zn Cd S∶ Cu QDs with blue Ga N chips,a high color rendering white LED was fabricated. The resulting three-band RGB QD-white LED exhibits high performance with luminous efficacy of 71 lm / W,color rendering index up to 94,CIE-coordinates of( 0. 352 4,0. 365 1),and color temperature of 4 788 K. Based on the changes in the photoluminescence lifetimes of Cu-doped QDs,it is found that the energy transfer process from green Zn In S∶ Cu QDs to red Zn Cd S∶ Cu QDs can be negligible,because the red QDs had no absorption at green band. These results suggest that Cu-doped QDs are promising for solid state lighting.

The photoluminescence(PL) spectra of ZnCuInS quantum dots(QDs) were measured in the temperature range from 100 to 300 K.The temperature dependences of the PL energy,linewidth,and intensity of the ZnCuInS QDs were investigated in detail.An anomalous increase in band gap of ZnCuInS QDs with temperature was observed.The full width at half maximum of the PL and thermal activation energy Ea of ZnCuInS QDs were 300 and 100 meV,respectively.These results suggested that the PL in the ZnCuInS QDs originated from the recombination of many kinds of defect-related emission centers in the interior and on the surface of the QDs.

The effect of mercaptopropionic acid(MPA) molecules on the charge transfer process from the quantum dots to ZnO nanocrystal films was studied in this paper by the steady-state and time-resolved photoluminescence spectroscopy.The obtained high efficiently photoluminescent CdSe-core CdS/ZnS-multishell quantum dots with few defects are air stable in quantum dot based devices.Three samples were prepared to make the measurements of time-resolved photoluminescence spectra,CdSe quantum dots film,CdSe quantum dots spun cast on ZnO nanocrystal film(CdSe/ZnO),and MPA molecules linked CdSe quantum dots and ZnO nanocrystal film(CdSe/MPA/ZnO).The shortening of photoluminescence life times of CdSe quantum dots deposited on ZnO nanocrystal films with and without MPA molecules indicated the electron transfer process happened in the interface between CdSe quantum dots and ZnO nanocrystals.But the decreased rate of electron transfer from CdSe quantum dots to ZnO nanocrystal films with MPA molecules was found,compared to the electron transfer rate of the CdSe/ZnO sample.Considering the fact that MPA molecules did not improve the charge transfer process from CdSe quantum dots to ZnO nanocrystal films,it was indicated that the MPA molecules was not a good choice in CdSe quantum dot sensitized solar cell.The experimental result suggested that the direct adsorption of CdSe quantum dots on metal oxide nanocrystal films would obtain quantum dot sensitized solar cell with higher power conversion efficiency.