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研究了在CdSe/ZnSe自组装量子点中CdSe量子点的发光随着激发光强度变化的特性。发现当激发强度(I)变化3个数量级的时候,量子点发光的峰位、峰形都没有发生明显的变化。通过公式L∝Ik(其中I是激发光强度,L是量子点发光强度,k是非线性系数)得到非线性系数k值。实验结果表明:在温度由21 K升高到300 K的过程中,k值随温度变化可以分为3个区域:当温度低于120 K时,k值接近于1;然后,随着温度升高,k值慢慢变小;最后,随温度进一步升高,k值由200 K时的0.946迅速减少到0.870。结合发光随温度变化的实验结果,确认在120 K以下发光主要来源于束缚激子复合。在温度由200 K升高到300 K的过程中,非线性系数的单调减小主要归因于随着温度的升高,发光部分来自于由自由电子或空穴到束缚态能级(FB)的复合。进一步通过分析量子点发光的积分强度随着温度的变化的实验结果,发现发光强度随温度升高而减弱的主要原因是材料中的缺陷或者位错等提供非辐射渠道。
The characteristics of CdSe QDs’ luminescence with the intensity of excitation light in CdSe / ZnSe self-assembled quantum dots were studied. It is found that when the excitation intensity (I) changes by 3 orders of magnitude, the peak position and the peak shape of the quantum dots do not change obviously. The value of the nonlinear coefficient k is obtained by the formula LαIk (where I is the intensity of the excitation light, L is the quantum dot luminous intensity, and k is a nonlinear coefficient). The experimental results show that in the process of increasing the temperature from 21 K to 300 K, the value of k can be divided into three regions with the change of temperature: when the temperature is lower than 120 K, the value of k is close to 1; then, as the temperature rises High and k values gradually decrease. Finally, as the temperature increases further, the k value decreases rapidly from 0.946 at 200 K to 0.870. Combined with the experimental results of luminescence with temperature, it is confirmed that the luminescence below 120 K mainly comes from the bound exciton recombination. The monotonous decrease of the nonlinear coefficient is mainly attributed to the increase of the temperature from 200 K to 300 K, the luminescence part comes from the free electrons or holes to the bound state level (FB) Compound. Furthermore, by analyzing the experimental results of the change of integral intensity of quantum dots with temperature, it is found that the main reason for the decrease of luminescence intensity with increasing temperature is that non-radiation channels are provided by defects or dislocations in the material.