Fabrication and optical properties of CuInS2 quantum dots

Quantum dots have excellent optical properties such as broad excitation spectra, tunable emission spectra, large Stokes shift, quantum-enhanced luminescence efficiency and so on. In this work, CuInS2 quantum dots were prepared successfully by utilizing the non-thermal injection method. They had diameters in the range of 2 similar to 4 nm. The average diameter of the dots was about 2.4 nm. The dominant wavelength in the emission spectrum was approximately 660 nm. However, the luminous intensity was relatively low. The sizes, compositions, and the surface states of the quantum dots were changed and controlled by coating a layer of ZnS on the dots or by varying the preparation temperature, the temperature holding time, and the molar ratio of Cu:In in the source materials. The luminous properties of the quantum dots were changed accordingly. The dominant wavelength in the emission spectrum was then tunable in the range of 600-690 nm. The as-grown quantum dots were coated with a thick layer of organics. The organic coatings prevented the aggregation of the quantum dots effectively. The organic layers may be a problem in many cases. The organic layer can be removed by suitable cleaning processes. But the cleaning process had no significant effect on the fluorescence spectrum of the quantum dots.