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Issue 46, 2016
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Towards understanding the unusual photoluminescence intensity variation of ultrasmall colloidal PbS quantum dots with the formation of a thin CdS shell

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Abstract

In this study, we report anomalous size-dependent photoluminescence (PL) intensity variation of PbS quantum dots (QDs) with the formation of a thin CdS shell via a microwave-assisted cation exchange approach. Thin shell formation has been established as an effective strategy for increasing the PL of QDs. Nonetheless, herein we observed an unusual PL decrease in ultrasmall QDs upon shell formation. We attempted to understand this abnormal phenomenon from the perspective of trap density variation and the probability of electrons and holes reaching surface defects. To this end, the quantum yield (QY) and PL lifetime (on the ns–μs time scales) of pristine PbS QDs and PbS/CdS core/shell QDs were measured and the radiative and non-radiative recombination rates were derived and compared. Moreover, transient absorption (TA) analysis (on the fs–ns time scale) was performed to better understand exciton dynamics at early times that lead to and affect longer time dynamics and optical properties such as PL. These experimental results, in conjunction with theoretical calculations of electron and hole wave functions, provide a complete picture of the photophysics governing the core/shell system. A model was proposed to explain the size-dependent optical and dynamic properties observed.

Graphical abstract: Towards understanding the unusual photoluminescence intensity variation of ultrasmall colloidal PbS quantum dots with the formation of a thin CdS shell

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Supplementary files

Article information


Submitted
21 Aug 2016
Accepted
27 Oct 2016
First published
27 Oct 2016

Phys. Chem. Chem. Phys., 2016,18, 31828-31835
Article type
Paper

Towards understanding the unusual photoluminescence intensity variation of ultrasmall colloidal PbS quantum dots with the formation of a thin CdS shell

F. Ren, S. A. Lindley, H. Zhao, L. Tan, B. A. Gonfa, Y. Pu, F. Yang, X. Liu, F. Vidal, J. Z. Zhang, F. Vetrone and D. Ma, Phys. Chem. Chem. Phys., 2016, 18, 31828
DOI: 10.1039/C6CP05786A

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