Origins of the Stokes Shift in PbS Quantum Dots: Impact of Polydispersity, Ligands, and Defects
Name
acsnano.8b00132.pdf
Description
Accepted version
Size
1.78 MB
Format
Adobe PDF
Checksum (MD5)
d19ec72f6b418fef40bd5f0359c6eb36
Author(s)
Liu, Yun
Kim, Donghun
Morris, Owen P
Zhitomirsky, David
Grossman, Jeffrey C
Date Issued
2018
Journal
ACS Nano
Publisher
American Chemical Society (ACS)
Version
Author's final manuscript
Abstract
© 2018 American Chemical Society. Understanding the origins of the excessive Stokes shift in the lead chalcogenides family of colloidal quantum dots (CQDs) is of great importance at both the fundamental and applied levels; however, our current understanding is far from satisfactory. Here, utilizing a combination of ab initio computations and UV-vis and photoluminescence measurements, we investigated the contributions to the Stokes shift from polydispersity, ligands, and defects in PbS CQDs. The key results are as follows: (1) The size and energetic disorder of a polydisperse CQD film increase the Stokes shift by 20 to 50 meV compared to that of an isolated CQD; (2) Franck-Condon (FC) shifts increase as the electronegativities of the ligands increase, but the variations are small (<15 meV). (3) Unlike the aforementioned two minor factors, the presence of certain intrinsic defects such as VCl+ (in Cl-passivated CQDs) can cause substantial electron density localization of the band edge states and consequent large FC shifts (100s of meV). This effect arising from defects can explain the excessive Stokes shifts in PbS CQDs and improve our understanding of the optical properties of PbS CQDs.
MIT Department
Massachusetts Institute of Technology. Department of Materials Science and Engineering
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DOI of Published Version
https://doi.org/10.1021/ACSNANO.8B00132
