Optical and conductivity properties of PbS nanocrystals in amorphous zirconia sol-gel films

Lead sulfide (PbS) nanocrystals (NCs), embedded in amorphous zirconia sol-gel film with different PbS mole concentration (5-30%), were grown at temperature, ranging from 200degreesC to 350degreesC. The size of PbS NCs was determined by TEM and by blue shift of the absorption edge. The size increased with an increase of the synthesis temperature and PbS mole concentration. The optical and electrical properties of various sizes of PbS NCs in zirconia film are investigated utilizing absorption, photoluminescence (PL) and current-voltage measurement. The PL spectra were Stokes shifted from the corresponding absorption edge by about 0.5 eV. The latter can be associated with recombination process from surface state. The electrical properties were investigated by the deposition of the PbS NCs-zirconia films on ITO/glass substrate, followed by their coverage with gold contact. The current-voltage characteristics depend on the PbS NCs size and exhibits nonlinear nearly symmetric curve, associated with the space-charge limited current or the tunneling of carriers through the nanocrystalline film.