Effects of Size and Capping Reagents on Biexciton Auger Recombination Dynamics of CdTe Quantum Dots
Effects of Size and Capping Reagents on Biexciton Auger Recombination Dynamics of CdTe Quantum Dots
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DOI：
10.1021/jp9018537
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发表时间：
2009-05
影响因子：
3.7
通讯作者：
Yoichi Kobayashi;Lingyun Pan;N. Tamai
中科院分区：
文献类型：
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作者：
Yoichi Kobayashi;Lingyun Pan;N. Tamai
以油酸（OA）和巯基乙酸（HS-CH2COOH， TGA）为封盖剂，合成了CdTe量子点（QDs）。通过改变激发强度，利用飞秒瞬态吸收光谱研究了CdTe量子点的双激子俄歇复合。分析了双激子俄歇复合τ俄歇的寿命与QD直径D和封盖剂的关系。发现τ俄歇值与Dα成正比，结垢指数α依赖于封盖试剂和/或表面条件。对于TGA封顶的CdTe量子点，α值为4.6，而对于OA封顶的CdTe量子点，α值为7.0，发光量子产率Φ为60 ~ 85%。这种关系并不适用于小尺寸的OA封顶CdTe量子点，其Φ相当低，为15 - 30%，其中τ俄歇与直径无关，短至2 ~ 3ps。这些结果表明，CdTe量子点的双激子俄歇复合强烈依赖于量子点表面捕获和封盖试剂。
CdTe quantum dots (QDs) were synthesized using oleic acid (OA) and thioglycolic acid (HS-CH2COOH, TGA) as capping reagents. Biexciton Auger recombination of CdTe QDs was examined by femtosecond transient absorption spectroscopy by changing excitation intensity. The lifetime of biexciton Auger recombination τAuger was analyzed as a function of QD diameter D and capping reagents. It was found that τAuger is proportional to Dα, and that the scaling index α is dependent on capping reagents and/or surface conditions. For TGA capped CdTe QDs, α is determined to be 4.6, whereas it is 7.0 for OA capped CdTe QDs with high luminescence quantum yields Φ of 60−85%. This relationship did not hold for small size OA capped CdTe QDs with rather low Φ of 15−30%, in which τAuger became as short as 2∼3 ps irrespective of the diameter. These results suggest that biexciton Auger recombination of CdTe QDs is strongly dependent on the QD surface trapping and capping reagents.