Size And Shape Control Of PbSe QDs And Research On Its Thermal Stability

PbSe quantum dots?QDs?are widely used in optoelectronic devices such as solar cells,photodetectors because of their strong quantum confinement effect,efficient multi-exciton generation?MEG?effect and wide spectral regulation range.Because the photoelectric properties of QDs are closely related to their size and shape,and the wide-spectrum photoelectric conversion has gradually become the focus of research in the field of solar cells,so the synthesis of PbSe QDs with monodispersity,wide spectral control range,controllable shape and uniform size distribution is still a hot research topic.However,PbSe QDs are extremely sensitive to air and unstable,which greatly limits their applications in optoelectronic devices.Therefore,it is urgent to find a method to effectively passivate the defect states on the surface of PbSe QDs in order to improve their stability in air.Based on the above problems,a new synthesis method is proposed in this paper.By in-situ tuning the reactivity of selenium source method,a ultralarge-scale?23.5 g?,wide range size?the first exciton absorption peak is adjustable at 717²300 nm,and the diameter of the corresponding QDs is 2⁸ nm?PbSe QDs and Nanocubes are synthesized.At the same time,The PbSe QDs synthesized by this method show excellent thermal stability in air.The main research results of this paper are as follows:1.Specifically,adopting PbCl₂-OLA as lead precursor,using two different reactivity of selenium sources,the first exciton absorption peak of PbSe quantum dots with adjustable in the range of 717²100 nm could be obtained by adjusting injection temperature,growth temperature and time,and the number of times of selenium source injection.2.The above synthetic methods have good universality,and a series of CdSe and ZnSe QDs with different sizes can be synthesized by using the two different reactivity of selenium sources.3.Small-sized PbSe nanocubes with a size of about 8 nm have been synthesized.By monitoring the absorption spectra and shape evolution of PbSe QDs,we analyzed the growth kinetics mechanism of PbSe from quantum dots to nanocubes.At the same time,the shape evolution may cause changes in the electronic structure of QDs and then affect the electronic transition.4.Because the stability of PbSe quantum dots is very important for device applications,we systematically studied the thermal stability of a series of PbSe quantum dots with different sizes in air.Finally,we studied the in-situ heating of the quantum dots in vacuum under electron microscopy to observe their fusion process and analyze the mechanism.