Size Control of CsPbBr3 Quantum Dots by Aluminum Doping Enabling Single-Photon Emission
Objective In quantum communication,achieving efficient transmission and long-distance communication relies on an ideal single-photon source.CsPbBr3 quantum dots hold significant promise as single-photon sources due to their high probability of single-photon emission.Among the methods to enhance CsPbBr3 quantum dots'single-photon performance,size reduction is crucial.In this study,we synthesize CsPbBr3 quantum dots doped with varying concentrations of Al3+ions using a thermal injection method and systematically investigate their optical and material properties.The results demonstrate that Al3+ion doping effectively modulates the emission intensity and wavelength of CsPbBr3 quantum dots while enhancing the interaction of Pb—Br bonds,thus significantly improving their environmental stability.Moreover,by leveraging the smaller ionic radius of Al3+ions compared to Pb2+ions,Al3+ion doping effectively induces lattice contraction in CsPbBr3 quantum dots,leading to reduced size and enhanced size uniformity.Consequently,the reduced size enhances the quantum confinement effect,significantly improving single-photon emission performance.This study presents new strategies for optimizing perovskite quantum dot single-photon sources,advancing the development of perovskite single-photon sources.Methods We utilize a hot injection method to synthesize CsPbBr3 quantum dots and Al3+-doped CsPbBr3 quantum dots,ensuring high crystallinity and superior size uniformity.The method involves two steps.First,a mixture of cesium carbonate,oleic acid,and octadecene is heated for 2 h in an inert environment.To enhance the synthesis quality of quantum dots,an excess of oleic acid is added,resulting in a cesium oleate precursor that is soluble at room temperature.Second,a mixture of lead bromide,aluminum bromide,oleic acid,oleylamine,and octadecene is heated for 2 h in an inert environment.This is followed by the rapid injection of 0.4 mL of cesium oleate precursor.After allowing the reaction to proceed for 5 s,immediate cooling is achieved using an ice-water bath.Subsequently,well-dispersed quantum dot solutions are obtained through high-speed centrifugation.Throughout the synthesis process,quantum dots with different doping concentrations(Al/Pb molar ratios of 0∶1,1∶2,1∶1,2∶3,and 3∶2)are synthesized by controlling the amount of aluminum bromide added.Results and Discussions The prepared Al∶CsPbBr3 quantum dots can maintain the crystal structure of CsPbBr3 quantum dots within a specific concentration range of Al3+ions,successfully introducing the energy level of Al3+ions.The addition of Al3+ions enhances the interaction of Pb—Br bonds in CsPbBr3 quantum dots and significantly improves their stability(Fig.2).Notably,while maintaining the crystal morphology of CsPbBr3 quantum dots,Al∶CsPbBr3 quantum dots exhibit reduced size and improved size uniformity.This is due to the substitution of larger Pb2+ions by smaller Al3+ions(Fig.3).Furthermore,fluorescence and absorption spectral analysis reveals that Al3+ions effectively enhance the optical properties of CsPbBr3 quantum dots,significantly increasing their fluorescence intensity.Importantly,CsPbBr3 quantum dots and Al∶CsPbBr3 quantum dots exhibit the same emission linewidth and demonstrate good environmental stability(Fig.5).These improvements broaden the potential applications of Al∶CsPbBr3 quantum dots across various fields.Conclusions In the paper,we successfully prepare Al∶CsPbBr3 quantum dots using a hot injection method and comprehensively investigate the influence of Al3+ions on the properties of CsPbBr3 quantum dots.The results from fluorescence spectra and absorption spectra indicate an effective enhancement in the fluorescence intensity of the quantum dots.With an increasing Al/Pb ratio,both the fluorescence and absorption spectra of the quantum dots exhibit a blue shift.However,when the Al/Pb ratio reaches 3∶2,the emission and absorption wavelengths unexpectedly undergo a red shift.Combined with X-ray diffractometer(XRD)data,this suggests that while a small amount of Al3+ions improves the optical properties of CsPbBr3 quantum dots,an excessive amount disrupts their crystal structure.X-ray photoelectron spectroscopy(XPS)data demonstrate that the introduction of Al3+ions shifts the Pb and Br energy levels of CsPbBr3 quantum dots towards higher binding energies,enhancing Pb—Br bond interaction and thereby improving stability.Moreover,single quantum dot excitation tests comparing CsPbBr3 quantum dots and Al∶CsPbBr3 quantum dots(Al/Pb molar ratio of 1∶1)reveal distinct fluorescence blinking characteristics.The g2(0)values suggest that Al∶CsPbBr3 quantum dots(Al/Pb molar ratio of 1∶1)demonstrate superior single-photon performance,attributed to the effective reduction in quantum dot size,improved size uniformity,and enhanced quantum confinement effects upon the introduction of Al3+ions.This study offers new experimental insights and methods for the preparation of perovskite quantum dots and the optimization of their quantum light source performance.
NETL
NSTL
万方数据
