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为了获得纳米晶之间以及单个纳米晶内部本体态至缺陷态两种能量转移在不同温度下对发光强度的影响,测量了碲化镉纳米晶层发光光谱随温度(78~300K)的变化情况.碲化镉纳米晶层发光光谱显示:碲化镉纳米晶层在低温下有明显的本体(约520nm)和缺陷(约605nm)发光,且发光强度随温度的改变呈现出不同的变化规律.在温度变化的第一阶段(78~140K),大尺寸碲化镉纳米晶发光效率高、表面缺陷少,小尺寸纳米晶至大尺寸纳米晶间的能量转移使得纳米晶本体发光强度逐渐升高、缺陷发光强度迅速降低.在温度变化的第二阶段(140~300K),随着温度的升高,无辐射跃迁几率的增大使得碲化镉纳米晶缺陷态和本体态发光强度均逐渐降低.因此,能量转移仅在温度变化的第一阶段对发光强度的影响起主要作用,在第二阶段起次要作用.为了进一步验证能量转移对发光强度的影响,将碲化镉纳米晶用聚乙二醇包裹以减少纳米晶间的能量转移;将纳米晶层的干燥过程放在近真空环境下进行以减少单个纳米晶内部本体至缺陷态的能量转移.光谱结果显示在温度变化的第一阶段,这两种方式下得到的纳米晶层发光强度均逐渐降低,能量转移对发光强度的影响不再起主要作用.证实了能量转移对发光强度的影响规律的合理性.
In order to obtain the effect of energy transfer on the luminescence intensity at different temperatures between nanocrystals and single nanocrystals, the luminescence spectra of CdTe nanocrystals were measured with the temperature (78 ~ 300K) The luminescence spectra of CdTe nanocrystalline layer show that the CdTe nanocrystalline layer has obvious bulk (about 520nm) and defects (about 605nm) luminescence at low temperature, and the luminescence intensity shows different variation with temperature. In the first stage of temperature change (78 ~ 140K), large size CdTe nanocrystals have high luminous efficiency and few surface defects. The energy transfer between small nanocrystals and large nanocrystals gradually increases the luminescence intensity of the nanocrystal bulk , The luminescence intensity of the defects rapidly decreases.With the increase of the temperature in the second stage of temperature change (140 ~ 300K), the increase of the probability of nonradiative transition makes the CdTe nanocrystal defect state and the bulk state luminescence intensity reduce gradually . Therefore, the energy transfer plays a major role on the luminescence intensity only in the first phase of temperature change and plays a secondary role in the second phase.In order to further verify the effect of energy transfer on the luminescence intensity, cadmium telluride The nanocrystal is encapsulated with polyethylene glycol to reduce the energy transfer between the nanocrystals and the nanocrystalline layer is dried in a near vacuum to reduce the energy transfer from the internal bulk to the defect state of a single nanocrystal.The spectral results show that at temperature In the first phase of the change, the luminescence intensity of the nanocrystalline layer decreased gradually under the two methods, and the influence of energy transfer on the luminescence intensity no longer played a major role. The rationality of energy transfer on the luminescence intensity was verified.