Preparation And Optical Properties Of PbSe/Pb_1-xSr_xSe QDs Embedded In Silicate Glass

IVA-VIA?PbS,PbSe,etc.?semiconductors have narrow band gaps and large exciton Born radius,which in turn exhibits excellent performance in optical and electrical properties,making their quantum dots?QDs?embedded in glass has potential and broad applications in laser sources,biological applications and near-infrared luminescent materials.For PbSe QDs,the effective band gap is 0.28 eV,and the exciton Boll radius is 46 nm,which makes the QDs have tunable photoluminescence from near-infrared to mid-infrared.Due to the quantum confinement effect,the photoluminescence band can be adjusted by changing the size of QDs,but when the size of QDs is too small or too large,its stability,particle size distribution and photoluminescence properties are not ideal.In this paper,the gradient alloy QDs were prepared by chemical method to extend the range of the photoluminescence band of QDs embedded in glass and enhance the photoluminescence properties.The Pb1-xSrxSe QDs with different chemical compositions were prepared in glass,and the similarities and differences between the pure PbSe and Pb1-xSrxSe QDs were studied.The photoluminescence enhancement mechanism of the gradient structure Pb1-xSrxSe QDs was obtained.In this paper,PbSe and Pb1-xSrxSe QDs doped glasses were prepared by conventional melting method using silicate glass with excellent thermodynamics and chemical stability as matrix.In this experiment,the stability of silicate glass matrix was studied and discussed,and PbSe QDs with various size were prepared by heat treatment.Then,by introducing SrO into the glass,Pb1-xSrxSe QDs were precipitated in the glass after heat treatment.The crystallization and chemical composition of Sr²⁺-doped PbSe QDs were analyzed by XRD and TEM.Finally,the optical properties,photodarkening and anti-Stokes photoluminescence of PbSe and Pb1-xSrxSe QDs were compared and analyzed by absorption spectra and photoluminescence spectra under different excitation conditions.The results are shown below:?1?PbSe quantum dots were prepared by a melting method in silicate glass.The composition of the glass was 50SiO₂-25Na₂O-8.2ZnO-10BaO-5Al₂O₃-1.2ZnSe-0.6PbO?mol%?.The calculated value of the Hruby constant of the experimental glass was 0.458.It is indicated that the silicate glass substrate grown as a PbSe quantum dot has good stability.After 490-540?/10h heat treatment,the PL peaks wavelength of the QDs moves from 1104 nm to 2185 nm,which realizes the adjustable PL from near infrared to mid-infrared.?2?PbSe QDs glass was heat treated at 500?,520? and 540? for 1²0 h,respectively.It was found that PbSe QDs have different growth indexes at different heat treatment temperatures,and the growth indexes at different heat treatment temperatures were obtained.These are 0.21,017 and 0.11,which are less than 1/3 of the Lifshitz-Slyozov-Wagner theory.Low-concentration precursors and diffusion-controlled growth methods result in smaller growth indices of QDs in the glass.?3?Pb_1-xSr_xSe QDs were formed by heat treatment after replacing BaO with 0-10mol%SrO in the glass composition.Duo to Sr²⁺increases its band gap after entering PbSe QDs,the absorption and PL bands of Pb1-xSrxSe QDs are significantly blue-shifted with respect to PbSe.At 520?/10h heat treatment,the absorption spectrum moves from1535 nm to 947 nm,and the PL spectrum shifts from 1578 nm to 1184 nm.The results of transmission electron microscopy and EDS showed that Sr²⁺entered the PbSe lattice and formed Pb_1-xSr_xSe QDs.?4?The PbSe and Pb_1-xSr_xSe QDs were excited by laser at 1319 nm and 1532 nm to realize the defect level photoluminescence.The PbSe QDs were excited by laser at1319 nm,when the laser intensity is higher than 700 mW,the the defect states PL appears photodarkening.The PbSe QDs are excited by the wavelength of 1532 nm,when the laser intensity is higher than 800 mW,the the defect states PL appears photodarkening.However,the Pb1-xSrxSe QDs showed no photodarkening at the two wavelengths of laser and the PL at different excitation intensities,indicating that the Pb_1-xSr_xSe QDs have stronger resistance to photodarkening,and that Sr²⁺enters PbSe.The QDs have a passivation effect on the defects on the surface of the QDs.?5?The anti-Stokes PL of Pb_1-xSr_xSe QDs was realized by using 1532 nm wavelength laser to excite different sizes of QDs.The integrated intensity of the anti-Stokes PL was linear with the excitation intensity,indicating that the anti-Stokes PL belongs to the phonon-assisted one-photon process.And it found that this anti-Stokes PL has size dependent.Based on the above data,a reasonable model is proposed,which explains the normal PL of Pb1-xSrxSe QDs excited by 800 nm wavelength.At the same time,it shows the surface trap energy of Se and Pb dangling bonds on the surface of the QDs.Stage and defect levels are responsible for carrier trapping and successfully explain the formation of anti-Stokes PL of Pb_1-xSr_xSe QDs and the size dependence of their PL.