Photoluminescence and far-infrared spectroscopy of PbS quantum dots – Polyvinyl alcohol nanocomposite

The nanocomposite consisting of PbS quantum dots with average diameter of 26 Å and polyvinyl alcohol was characterized using photoluminescence and far-infrared spectroscopy. Photoluminescence spectra of nanocomposite, measured in temperature range from 8 to 280 K, consists of broad peak which spans the energy range from 1.2 to 2.1 eV and can be connected with trap states inside the band gap. Far-infrared measurements are consistent with theoretical calculations that include mechanical boundary conditions at the quantum dot – host interface. Observed peak at 90 cm−1 can be assigned to coupled modes with lp = 1, while broad peak at 275 cm−1 is above any lattice frequency and is close to sum of the frequencies of the lp = 0 acoustic and lp = 0 coupled optical mode of PbS quantum dots.