Optoelectronic Materials Section, Department of Chemical Engineering, Delft University of Technology , Julianalaan 136, 2628 BL Delft, The Netherlands.
Nano Lett. 2013 Sep 11;13(9):4380-6. doi: 10.1021/nl402223q. Epub 2013 Aug 23.
The cooling and Auger recombination of electron-hole pairs in PbSe quantum dots (QDs) and a series of nanorods (NRs) with similar diameter and varying length was studied by ultrafast pump-probe laser spectroscopy. Hot exciton cooling rates are found to be independent of nanocrystal shape. The energy relaxation rate decreases during cooling of charges, due to reduction of the density of electronic states. Auger recombination occurs via cubic third-order kinetics of uncorrelated charges in the QDs and NRs with length up to 29 nm. On increasing the NR length to 52 nm, a crossover to bimolecular exciton decay is found. This suggests a spatial extent of the one-dimensional exciton of 30-50 nm, which is significantly smaller than the value of 92 nm for the three-dimensional exciton diameter in bulk PbSe. The Auger decay time increases with NR length, which is beneficial for applications in nanocrystal lasers as well as for generation of free charges in photovoltaics.
通过超快泵浦探针激光光谱学研究了 PbSe 量子点 (QD) 和一系列具有相似直径和不同长度的纳米棒 (NR) 中电子-空穴对的冷却和俄歇复合。发现热激子冷却速率与纳米晶体形状无关。在冷却电荷的过程中，能量弛豫速率降低，这是由于电子态密度的降低。俄歇复合通过 QD 和 NR 中不相关电荷的立方三阶动力学发生，NR 的长度可达 29nm。当 NR 长度增加到 52nm 时，发现会发生双分子激子衰减的交叉。这表明一维激子的空间扩展为 30-50nm，明显小于体相 PbSe 中三维激子直径的 92nm 值。俄歇衰减时间随 NR 长度的增加而增加，这有利于在纳米晶体激光器中的应用以及在光伏中产生自由电荷。
