Photluminescence properties of orgainic-inorganic sol-gel films doped with semiconductor quantum dots

Hybrid organic-inorganic thin films doped with lead sulfide nanocrystallites were synthesized by a combination of colloidal chemistry and sol-gel processing. In order to study the influence on the spectroscopic properties of the crystallite surface, and hence the related defect states, PbS-doped films with different sulfur to lead ratios and different surface capping agent concentrations were fabricated. X-ray diffraction measurements showed the presence of nanoparticles with a mean diameter raging from 3 to 5 nm. The absorption spectra showed a large blue shift of the absorption edge to shorter wavelength, indicating strong quantum confinement. Strong photoluminescence emission in the near infrared was found by pumping at 514 or 532 nm. The emission intensity and its position were found to be dependent on the elaboration parameters. The film fabrication process influences only slightly the good particle size distribution of the colloidal PbS solutions. Best results were obtained for films with low sulfur to lead ratio or with high capping agent concentration.