Matrix and thermal effects on photoluminescence from PbS quantum dots

Abstract

Lead sulfide nanoquantum dot samples were prepared with sol gel materials, a capping agent, and with various concentrations of PbS quantum dots. The –OH group absorption was significantly reduced during the heating process. The calculated quantum dot sizes were 1.2 nm for undoped sol gel and 0.97 nm for zirconium-doped sol gel. Without a capping agent, no photoluminescence was observed for a wide range of PbS particle concentrations. Strong photoluminescence was achieved with a capping agent when excited by a 480 nm wavelength xenon light source at room temperature. Luminescence quenching was observed with an extra –SH group from the matrix and excess H2S exposure. The quenching process typically broadened the spectra and blueshifted the peak when there was excess sulfur. The band gap energy was shifted from 1.64 to 1.68 eV for the zirconium-doped samples and 1.54–1.56 eV for the zirconium-free samples at room temperature. The thermal process significantly enhanced the luminescence intensity and redshifted the peak. The peak shift was 1.64–1.53 eV for zirconium-doped samples and 1.54–1.49 eV for zirconium-free samples.