Anomalous Independence of Multiple Exciton Generation on Different Group IV-VI Quantum Dot Architectures

作者：Trinh M Tuan; Polak Leo; Schins Juleon M; Houtepen Arjan J; Vaxenburg Roman; Maikov Georgy I; Grinbom Gal; Midgett Aaron G; Luther Joseph M; Beard Matthew C; Nozik Arthur J; Bonn Mischa; Lifshitz Efrat; Siebbeles Laurens D A^*

来源：Nano Letters, 2011, 11(4): 1623-1629.

DOI：10.1021/nl200014g

• Multiple exciton generation
• hot exciton cooling
• Auger recombination
• quantum dot architecture

Multiple exciton generation (MEG) in PbSe quantum dots (QDs), PbSexS1-x alloy QDs, PbSe/PbS core/shell QDs, and PbSe/ PbSeyS1-y core/alloy-shell QDs was studied with time-resolved optical pump and probe spectroscopy. The optical absorption exhibits a red-shift upon the introduction of a shell around a PbSe core, which increases with the thickness of the shell. According to electronic structure calculations this can be attributed to charge delocalization into the shell. Remarkably, the measured quantum yield of MEG, the hot exciton cooling rate, and the Auger recombination rate of biexcitons are similar for pure PbSe QDs and core/shell QDs with the same core size and varying shell thickness. The higher density of states in the alloy and core/shell QDs provide a faster exciton cooling channel that likely competes with the fast MEG process due to a higher biexciton density of states. Calculations reveal only a minor asymmetric delocalization of holes and electrons over the entire core/shell volume, which may partially explain why the Auger recombination rate does not depend on the presence of a shell.

• 出版日期2011-4