硒铟银锌四元量子点的制备及光学性能研究

发布时间：2018-07-05 19:39

本文选题：量子点 + 荧光衰减寿命　；参考：《天津理工大学》2017年硕士论文

【摘要】：量子点由于其光谱可调谐,发光效率高,是近年来发展起来的一类新型功能材料,在发光器件、光催化、生物成像、光伏电池、传感器以及激光等领域中均有着非常广泛的应用。目前通常采用的调节发射光谱范围的手段有改变量子点颗粒尺寸,改变组分等方法。本文采用热注入法制备了不同粒径的ZnAg InSe量子点及不同Zn/Ag前驱物配比的ZnxAgInSe量子点,同时合成了包覆ZnSe壳层的ZnAgInSe/ZnSe量子点。通过荧光衰减寿命、变温PL的测试分析了其内部发光机制。具体内容如下:通过热注入法制备了不同颗粒尺寸的ZnAgInSe量子点。受量子尺寸效应的影响,随着颗粒尺寸的增加发光强度明显增强且光谱发生红移。通过进一步测试荧光衰减寿命来研究其内部的发光机制,主要是由导带到内部能级的复合,表面相关的复合以及施主-受主对复合三个过程共同作用的结果,且施主-受主对的复合占主要部分。同时,我们对不同颗粒尺寸的ZnAgInSe量子点测试了变温PL光谱,并研究了变温光谱的发射峰位置,发射峰强度以及半高宽与温度之间的变化关系。可以发现峰强度随着温度的升高而减弱,这可能是由于热激活非辐射复合机制引起的。ZnAgInSe量子点变温发射光谱的展宽可能是激子-声子的耦合导致的,黄昆因子随着颗粒尺寸的增加而增大,表明了激子-声子耦合作用增强。通过热注入法制备了不同组分的ZnxAgInSe(x=0.3,0.5,1)量子点,通过改变Zn/Ag配比成功的调节了量子点的发光峰范围。可以发现,随着Zn/Ag配比的增加发射光谱发生了明显的蓝移,同时发光强度也相应的增强,表明量子点中Zn空位(VZn)和Ag空位(VAg)的数量发生了变化,Zn组分的增加引起了VAg的降低,而VZn相应的增加。我们进一步测试了ZnxAgInSe量子点的变温PL谱,并研究了发射峰位置,半高宽,峰强度随温度的变化关系。随着Zn/Ag配比的增加黄昆因子S逐渐降低,可能是由于晶格结构的热膨胀引起了带隙能量的变化。ZnxAgInSe量子点的发光机制可以描述为以下三个过程:导带到内部能级的复合,表面相关的复合以及施主-受主对复合,其中施主-受主对复合占主导地位。同时,我们进一步将ZnxAgInSe(x=1)量子点应用在了温度传感器中。通过热注入法制备了包覆不同ZnSe层数的ZnAgInSe/ZnSe量子点。随着ZnSe壳层数量的增加,发光峰位发生蓝移,且发光强度也逐渐增强。ZnAgInSe/ZnSe核/壳量子点的发光机制主要是由于导带到内部定域能级的复合、表面相关的复合以及施主-受主对复合,其中以施主-受主对的复合为主。通过测试变温光谱,研究了发射峰位置,发射峰强度以及半高宽与温度之间的变化关系。可以观察到在10 K到300 K的温度变化范围内,随着温度的升高强度减弱且峰位红移,光谱展宽。拟合得到黄昆因子S均小于1,说明其激子-声子的耦合较弱,且随着ZnSe层数的增加S逐渐降低,表明激子-声子耦合逐渐下降。
[Abstract]:Quantum dots, due to their tunable spectrum and high luminescence efficiency, are a kind of new functional materials developed in recent years, such as light-emitting devices, photocatalysis, biological imaging, photovoltaic cells, photovoltaic cells. Sensors and lasers are widely used in many fields. At present, the usual methods to adjust the range of emission spectrum include changing the particle size of quantum dots and changing the composition of quantum dots. In this paper, ZnAg InSe quantum dots with different particle sizes and ZnxAgInSe quantum dots with different Zn / Ag precursor ratios have been prepared by thermal injection method. ZnAgInSe/ ZnSe quantum dots coated with ZnSe shell have been synthesized at the same time. The internal luminescence mechanism was analyzed by the fluorescence decay lifetime and the measurement of variable temperature PL. The main contents are as follows: ZnAgInSe quantum dots with different particle sizes were prepared by thermal injection. Under the influence of quantum size effect, the luminescence intensity increases obviously with the increase of particle size and the spectrum is red-shifted. The fluorescence decay lifetime is further measured to study the internal luminescence mechanism, which mainly consists of the recombination from the conduction to the inner energy level, the surface dependent recombination and the interaction of the donor-acceptor with the recombination. And the combination of the donor-acceptor pair is the main part. At the same time, we measured the variable-temperature PL spectra of ZnAgInSe quantum dots with different particle sizes, and studied the position of the emission peak, the intensity of the emission peak and the relationship between the half-maximum width and the temperature of the variable-temperature spectra. It can be found that the peak intensity decreases with the increase of temperature, which may be due to the broadening of the variable-temperature emission spectra of the .ZnAgInSe quantum dots caused by the thermally activated non-radiative recombination mechanism, which may be caused by the exciton-phonon coupling. The Huang Kun factor increases with the increase of particle size, indicating that the exciton-phonon coupling is enhanced. ZnxAgInSe QDs with different compositions were prepared by thermal injection. The range of luminescence peaks of QDs was successfully adjusted by changing the ratio of Zn- / Ag. It can be found that with the increase of Zn / Ag ratio, the blue shift occurs and the luminescence intensity increases correspondingly, which indicates that the increase of Zn vacancy (VZn) and Ag vacancy (VAg) in quantum dots leads to the decrease of VAg. However, VZn increased accordingly. We have further measured the variable-temperature PL spectra of ZnxAgInSe quantum dots, and studied the dependence of the position of emission peak, the half-maximum width and the peak intensity with temperature. With the increase of Zn / Ag ratio, the Huang Kun factor S decreases gradually, which may be due to the change of band gap energy caused by the thermal expansion of lattice structure. The luminescence mechanism of ZnxAgInSe quantum dots can be described as the following three processes: the recombination of the conduction to the inner energy level. Surface-dependent recombination and donor-acceptor-pair recombination, in which the donor-acceptor pair is dominant. At the same time, we further apply ZnxAgInSe (x1) quantum dots to the temperature sensor. ZnAgInSe- / ZnSe quantum dots coated with different ZnSe layers were prepared by thermal injection. With the increase of the number of ZnSe shell layers, the blue shift of luminescence peak occurs and the luminescence intensity increases gradually. The luminescence mechanism of ZnAgInSe-ZnSe / shell quantum dots is mainly due to the recombination of the conduction to the inner localized energy level. Surface-dependent recombination and donor-acceptor-pair recombination, in which the donor-acceptor pair is the dominant. The relationship between the position of the emission peak, the intensity of the emission peak, and the half-maximum width of the emission peak was studied by measuring the variable-temperature spectra. It can be observed that in the range of 10 K to 300 K, the intensity decreases and the peak redshifts with the increase of temperature, and the spectrum broadens. The fitting results show that the Huang Kun factor S is less than 1, which indicates that the exciton-phonon coupling is weak and decreases with the increase of the number of ZnSe layers, indicating that the exciton-phonon coupling decreases gradually.
【学位授予单位】：天津理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O471.1

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