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Title: Origins of the Stokes Shift in PbS Quantum Dots: Impact of Polydispersity, Ligands, and Defects

Abstract

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.

Authors:
ORCiD logo [1]; ORCiD logo [2];  [1];  [1];  [1]
  1. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States). Dept. of Materials Science and Engineering
  2. Korea Inst. of Science and Technology, Seoul (Korea). Computational Science Research Center
Publication Date:
Research Org.:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). National Energy Research Scientific Computing Center (NERSC)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1488926
Grant/Contract Number:  
AC02-05CH11231
Resource Type:
Accepted Manuscript
Journal Name:
ACS Nano
Additional Journal Information:
Journal Volume: 12; Journal Issue: 3; Journal ID: ISSN 1936-0851
Publisher:
American Chemical Society (ACS)
Country of Publication:
United States
Language:
English

Citation Formats

Liu, Yun, Kim, Donghun, Morris, Owen P., Zhitomirsky, David, and Grossman, Jeffrey C. Origins of the Stokes Shift in PbS Quantum Dots: Impact of Polydispersity, Ligands, and Defects. United States: N. p., 2018. Web. doi:10.1021/acsnano.8b00132.
Liu, Yun, Kim, Donghun, Morris, Owen P., Zhitomirsky, David, & Grossman, Jeffrey C. Origins of the Stokes Shift in PbS Quantum Dots: Impact of Polydispersity, Ligands, and Defects. United States. doi:10.1021/acsnano.8b00132.
Liu, Yun, Kim, Donghun, Morris, Owen P., Zhitomirsky, David, and Grossman, Jeffrey C. Mon . "Origins of the Stokes Shift in PbS Quantum Dots: Impact of Polydispersity, Ligands, and Defects". United States. doi:10.1021/acsnano.8b00132. https://www.osti.gov/servlets/purl/1488926.
@article{osti_1488926,
title = {Origins of the Stokes Shift in PbS Quantum Dots: Impact of Polydispersity, Ligands, and Defects},
author = {Liu, Yun and Kim, Donghun and Morris, Owen P. and Zhitomirsky, David and Grossman, Jeffrey C.},
abstractNote = {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.},
doi = {10.1021/acsnano.8b00132},
journal = {ACS Nano},
number = 3,
volume = 12,
place = {United States},
year = {2018},
month = {2}
}

Journal Article:
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