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全无机钙钛矿量子点因其卓越光电特性受到广泛关注，但较差的稳定性限制其实际应用。近年来，致密无机玻璃网络中原位析出钙钛矿量子点(CsPbX3@glass)具有优异稳定性，然而大部分研究致力于优化钙钛矿量子点玻璃的光学性能，对其载流子动力学的研究较为匮乏。由此，本工作借助飞秒激光超快瞬态吸收光谱(fs-TAS)探索了由于晶化温度改变导致的缺陷变化与卤素比例变化对CsPb(Cl/Br)3@glass载流子动力学的影响。研究发现，随着热处理温度升高，更多Br~–从玻璃网络中扩散进入量子点晶格，导致CsPb(Cl/Br)3量子点电声耦合强度减弱，热载流子弛豫时间逐渐从140 fs增加至210 fs；当经历较高温度热处理(520℃)时，fs-TAS的基态漂白红侧(长波长方向)出现随时间衰减的负信号，证明新缺陷态存在，导致Cs Pb(Cl/Br)3@glass呈现特别长的荧光寿命。
Abstract：Introduction Inorganic perovskite quantum dots have attracted extensive attention due to their excellent optoelectronic properties,but the poor stability limits their practical applications.In recent years,perovskite quantum dots in situ crystallization inside robust inorganic glass network(Cs Pb X＿3@glass,X=Cl,Br,I) have been evidenced to have superior stability.However,most studies have focused on optimizing the optical properties,while few investigations aiming at carrier dynamics.What's more,we don't know if interesting phenomenon will happen to the carrier dynamics of perovskite quantum dot glasses,which obtain rare study of mechanism of carrier dynamics,and no halogen mixing are involved before.In this work,the influence of defects and halogen ratios induced by the elevation of crystallization temperature on the carrier dynamics of CsPb(Cl/Br)＿3@glass nanocomposites are investigated by means of femtosecond laser ultrafast transient absorption spectroscopy(fs-TAS).Methods We synthesized perovskite quantum dot glass by high temperature melting-heat treatment,showing final composition with proportions of(%,in mole) 30SiO-25B＿2O＿3-5Al＿2O＿3-5ZnO-5CaF＿2-2Pb Br＿2-4PbCl＿2-5Na Br-10Na Cl-9Cs＿2CO＿3.The raw materials are silica(SiO＿2,Bodie,analytical grade),alumina(Al＿2O＿3,Hengxing,99%),calcium fluoride(CaF＿2,McLean,99%),boron oxide(B＿2O＿3,McLean,98%),zinc oxide(ZnO,McLean,99%),cesium carbonate(Cs＿2CO＿3,McLean,98%),sodium bromide(NaBr,McLean,99%)and sodium iodide(NaCl,McLean,99.5%),which are used as raw materials to weigh,mix and grind in agate mortar.The resulting mixture was then placed in a sealed alumina crucible and melted at 1 200℃for 30 min in ambient atmosphere.Subsequently,the glass melt was poured into a copper mold at room temperature.Finally,the obtained bulk glass was treated at 480,500℃and520℃respectively for 10 h to induce the precipitation of perovskite quantum dots in the glass,thus obtaining glass ceramics containing perovskite quantum dots.Results and discussion TEM shows that perovskite quantum dots are precipitated in glass.With the increase of temperature of thermal treatment,XRD appears attenuated diffraction peak of perovskite quantum dots and shifts to a small angle,while PL spectrum and absorption peak red shift,which prove that Br～–has entered into the lattice.Subsequently,PLQY proved that high thermal treatment temperature could weaken radiation recombination,and the fluorescence attenuation curve shows an unusually long life.The transient absorption spectrum explores the whole carrier dynamics process.First,it is obtained that the hot carrier relaxation lifetimes of perovskite quantum dot glasses treated at 480,500℃and 520℃are 140,190 fs and 210 fs,respectively.The temperature related spectrum proves that the hot carrier relaxation becomes slower due to the weakening of electro-acoustic coupling.In the following process of exciton recombination,a new defect state can be observed on the transient absorption spectrum,which may be the reason of the abnormal life of high thermal treatment temperature.Conclusions In summary,with the increase of thermal treatment temperature,the electro-acoustic coupling strength decreases due to the entry of Br～–into the lattice.Meanwhile,the hot carrier relaxation takes longer period of time.In addition,due to the high treatment temperature,new shallow level defects that can capture electrons appear,and some electrons can be released back to the conduction band for radiation recombination.This eventually leads to a great improvement of fluorescence lifetime.Understanding these internal mechanisms may provide new guidance for synthesis and application of the investigated material.
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基本信息:
DOI：10.14062/j.issn.0454-5648.20230915
中图分类号:TQ171.1
引用信息:
[1]陈荣华,林继栋,陈树鑫,等.CsPb(Cl/Br)_3钙钛矿量子点玻璃的载流子动力学[J].硅酸盐学报,2024,52(08):2587-2597.DOI:10.14062/j.issn.0454-5648.20230915.
基金信息:
国家自然科学基金(52272141,51972060,12074068,52102159,22103013,12304442);; 福建省自然科学基金(2022J05091,2020J02017,2021J06021,2021J01190,2020J01931,2020H0026)
2024-04-30
2024-04-30
2024-04-30