Size-dependent Absorbtion And Photoluminescence Of PbS QDs Embedded In Silicate Glasses

Lead chalcogenide quantum dots(QDs)have attracted a lot of attention due to their small band gap and large exciton Bohr radius,which lead to strong quantum confinement effect.PbS quantum dots have good luminescence properties in the near infrared band.Moreover,by controlling the size of quantum dots,the absorption and emission spectra can be adjusted in the near infrared spectrum and the spectra can cover the whole transmission window of quartz optical fiber.Therefore,PbS quantum dots have attracted a lot of attention due to its great application value.Quantum dots doped glass has good thermal stability,chemical stability,high mechanical strength and can be made into a variety of optoelectronic devices.It has important application prospect in the field of Optoelectronic Information.The average particle size and size distribution of quantum dots have a strong influence on optical property of quantum dots doped glass.In this paper,PbSquantum dots doped silicate glasses were prepared by melt quenching method.The PbS quantum dots with narrow size distribution were synthesized by controlling the heat treatment.The effects of heat treatment regime and glass composition on the absorption and luminescence properties of PbS quantum dots were investigated by means of XRD,TEM,absorption spectra and PL spectra.The luminescent model of PbS quantum dots in glass was presented.Based on the composition of glass,especially the ratio of sulfur and lead in glass matrix,and the heat treatment system optimization,the average size of PbS quantum dots is between 1.27 nm and 7.32 nm,the size distribution of PbS quantum dots can be controlled from 4.91% to 10.00%,the narrow band absorption and fluorescence can be adjusted in 700-2500 nm.By adjusting the heat treatment conditions of the glass,the absorption peak and the luminescence peak of PbS quantum dots in the glass were in the range of 700 nm-2500 nm.With the increase of alkaline earth metal cycles,the crystallization temperature of the glass decreased and excess sulfur could promot the crystallization of PbS quantum dots.The PbS quantum dots with size distribution below 5 % were synthesized in glass.These quantum dots are mostly in the range of 3.2 nm-4.6 nm.The optimum heat treatment temperature in this experiment is from 520oCto 550 oC.The size distribution of quantum dots can be reduced by prolonging the heat treatment time.Due to the small size dispersion,most of the absorption spectra can be simulated using several Gaussian functions and they corresponded to the transition of electrons at different levels of PbS quantum dots.photoluminescence spectra of these PbS QDs can be nicely fitted using dual Gaussian functions.A defect model of PbS quantum dots in glass was proposed to explain the luminescence properties.