Interfacial Charge Separation and Recombination in InP and Quasi-Type II InP/CdS Core/Shell Quantum Dot-Molecular Acceptor Complexes

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• 作者：Kaifeng Wu ; Nianhui Song ; Zheng Liu ; Haiming Zhu ; William Rodr铆guez-C贸rdoba ; Tianquan Lian
• 刊名：The Journal of Physical Chemistry A
• 出版年：2013
• 出版时间：August 15, 2013
• 年：2013
• 卷：117
• 期：32
• 页码：7561-7570
• 全文大小：562K
• 年卷期：v.117,no.32(August 15, 2013)
• ISSN：1520-5215

文摘

Recent studies of group II鈥揤I colloidal semiconductor heterostuctures, such as CdSe/CdS core/shell quantum dots (QDs) or dot-in-rod nanorods, show that type II and quasi-type II band alignment can facilitate electron transfer and slow down charge recombination in QD鈥搈olecular electron acceptor complexes. To explore the general applicability of this wave function engineering approach for controlling charge transfer properties, we investigate exciton relaxation and dissociation dynamics in InP (a group III鈥揤 semiconductor) and InP/CdS core/shell (a heterostructure beween group III鈥揤 and II鈥揤I semiconductors) QDs by transient absorption spectroscopy. We show that InP/CdS QDs exhibit a quasi-type II band alignment with the 1S electron delocalized throughout the core and shell and the 1S hole confined in the InP core. In InP鈥搈ethylviologen (MV²⁺) complexes, excitons in the QD can be dissociated by ultrafast electron transfer to MV²⁺ from the 1S electron level (with an average time constant of 11.4 ps) as well as 1P and higher electron levels (with a time constant of 0.39 ps), which is followed by charge recombination to regenerate the complex in its ground state (with an average time constant of 47.1 ns). In comparison, InP/CdS-MV²⁺ complexes show similar ultrafast charge separation and 5-fold slower charge recombination rates, consistent with the quasi-type II band alignment in these heterostructures. This result demonstrates that wave function engineering in nanoheterostructures of group III鈥揤 and II鈥揤I semiconductors provides a promising approach for optimizing their light harvesting and charge separation for solar energy conversion applications.