Handle URI:
http://hdl.handle.net/10754/626080
Title:
Origins of Stokes shift in PbS nanocrystals
Authors:
Voznyy, Oleksandr; Levina, Larissa; Fan, Feng-Jia; Walters, Grant; Fan, James Z.; Kiani, Amirreza; Ip, Alexander H.; Thon, Susanna M.; Proppe, Andrew; Liu, Mengxia; Sargent, Edward H.
Abstract:
Stokes shift, an energy difference between the excitonic absorption and emission, is a property of colloidal quantum dots (CQDs) typically ascribed to splitting between dark and bright excitons. In some materials, e.g., PbS, CuInS2, CdHgTe, a Stokes shift of up to 200 meV is observed, substantially larger than the estimates of dark-bright state splitting or vibronic relaxations. The shift origin remains highly debated, as contradictory signatures of both surface and bulk character were reported for the Stokes-shifted electronic state. Here we show that the energy transfer among CQDs in a polydispersed ensemble in solution suffices to explain the excess Stokes shift. This energy transfer is primarily due to CQD aggregation, and can be substantially eliminated by extreme dilution, higher-viscosity solvent, or better-dispersed colloids. Our findings highlight that ensemble polydispersity remains the primary source of the Stokes shift in CQDs in solution, propagating into the Stokes shift in films and the open-circuit voltage deficit in CQD solar cells. Improved synthetic control can bring notable advancements in CQD photovoltaics, and the Stokes shift continues to provide a sensitive and significant metric to monitor ensemble size distribution.
Citation:
Voznyy O, Levina L, Fan F-J, Walters G, Fan JZ, et al. (2017) Origins of Stokes shift in PbS nanocrystals. Nano Letters. Available: http://dx.doi.org/10.1021/acs.nanolett.7b01843.
Publisher:
American Chemical Society (ACS)
Journal:
Nano Letters
KAUST Grant Number:
KUS-11-009-21
Issue Date:
27-Oct-2017
DOI:
10.1021/acs.nanolett.7b01843
Type:
Article
ISSN:
1530-6984; 1530-6992
Sponsors:
We thank Kyle Kemp, Janet Macdonald, Chih-Shan Tan and Kemar Reid for fruitful discussions. This publication is based in part on work supported by Award KUS-11-009-21, made by King Abdullah University of Science and Technology (KAUST), by the Ontario Research Fund Research Excellence Program, and by the Natural Sciences and Engineering Research Council (NSERC) of Canada Strategic Partnership Grant 478954-15.
Appears in Collections:
Publications Acknowledging KAUST Support

Full metadata record

DC FieldValue Language
dc.contributor.authorVoznyy, Oleksandren
dc.contributor.authorLevina, Larissaen
dc.contributor.authorFan, Feng-Jiaen
dc.contributor.authorWalters, Granten
dc.contributor.authorFan, James Z.en
dc.contributor.authorKiani, Amirrezaen
dc.contributor.authorIp, Alexander H.en
dc.contributor.authorThon, Susanna M.en
dc.contributor.authorProppe, Andrewen
dc.contributor.authorLiu, Mengxiaen
dc.contributor.authorSargent, Edward H.en
dc.date.accessioned2017-11-01T08:19:12Z-
dc.date.available2017-11-01T08:19:12Z-
dc.date.issued2017-10-27en
dc.identifier.citationVoznyy O, Levina L, Fan F-J, Walters G, Fan JZ, et al. (2017) Origins of Stokes shift in PbS nanocrystals. Nano Letters. Available: http://dx.doi.org/10.1021/acs.nanolett.7b01843.en
dc.identifier.issn1530-6984en
dc.identifier.issn1530-6992en
dc.identifier.doi10.1021/acs.nanolett.7b01843en
dc.identifier.urihttp://hdl.handle.net/10754/626080-
dc.description.abstractStokes shift, an energy difference between the excitonic absorption and emission, is a property of colloidal quantum dots (CQDs) typically ascribed to splitting between dark and bright excitons. In some materials, e.g., PbS, CuInS2, CdHgTe, a Stokes shift of up to 200 meV is observed, substantially larger than the estimates of dark-bright state splitting or vibronic relaxations. The shift origin remains highly debated, as contradictory signatures of both surface and bulk character were reported for the Stokes-shifted electronic state. Here we show that the energy transfer among CQDs in a polydispersed ensemble in solution suffices to explain the excess Stokes shift. This energy transfer is primarily due to CQD aggregation, and can be substantially eliminated by extreme dilution, higher-viscosity solvent, or better-dispersed colloids. Our findings highlight that ensemble polydispersity remains the primary source of the Stokes shift in CQDs in solution, propagating into the Stokes shift in films and the open-circuit voltage deficit in CQD solar cells. Improved synthetic control can bring notable advancements in CQD photovoltaics, and the Stokes shift continues to provide a sensitive and significant metric to monitor ensemble size distribution.en
dc.description.sponsorshipWe thank Kyle Kemp, Janet Macdonald, Chih-Shan Tan and Kemar Reid for fruitful discussions. This publication is based in part on work supported by Award KUS-11-009-21, made by King Abdullah University of Science and Technology (KAUST), by the Ontario Research Fund Research Excellence Program, and by the Natural Sciences and Engineering Research Council (NSERC) of Canada Strategic Partnership Grant 478954-15.en
dc.publisherAmerican Chemical Society (ACS)en
dc.titleOrigins of Stokes shift in PbS nanocrystalsen
dc.typeArticleen
dc.identifier.journalNano Lettersen
dc.contributor.institutionDepartment of Electrical and Computer Engineering, University of Toronto, 10 King’s College Road, Toronto, Ontario, M5S 3G4, Canadaen
dc.contributor.institutionDepartment of Electrical and Computer Engineering, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218-2608, USAen
kaust.grant.numberKUS-11-009-21en
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