Understanding the Occurrence of the Maximum Band-Edge Photoluminescence of TGA-Capped CdS QDs via Growth Kinetic Study

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• 作者：Xiaogang Xue ; Zanyong Zhuang ; Feng Huang ; Zhang Lin
• 刊名：Crystal Growth & Design
• 出版年：2013
• 出版时间：December 4, 2013
• 年：2013
• 卷：13
• 期：12
• 页码：5220-5228
• 全文大小：607K
• 年卷期：v.13,no.12(December 4, 2013)
• ISSN：1528-7505

文摘

The mechanism by which the maximum band-edge emission of quantum dots (QDs) occurs remains unclear. In this work, systematic kinetic studies revealed that the growths of thioglycolic acid (TGA)-capped CdS QDs at three concentrations (7.0, 2.3, and 0.8 mM) undergo a two-stage process: an initial oriented attachment (OA) dominant stage and a subsequent Ostwald Ripening (OR) stage. At the transition point from the OA dominant to the OR stage, the band-edge PL peaked at 450鈥?70 nm and reached its 鈥渕aximum鈥? with the narrowest peak width about 28 nm. Investigation on particle size distribution (PSD) showed size 鈥渇ocusing鈥?in the OA dominant stage. Nevertheless, the ideally narrowest PSD occurs far earlier than the maximum band-edge emission. Furthermore, its PL emission was found broadened by competitive defect-related emissions, reasonably assigned to lattice defects generated by the initial OA growth. Annealing of defects at the later OA stage can be responsible for enhanced PL band-edge emission to a certain maximum value, which will decrease in the subsequent OR growth due to the broadening PSD. The role of surface-capping was also discussed and proved to be the key factor to achieve the maximum band-edge emission of QDs by tuning the crystal growth kinetics.