Quantum confinement-tunable ultrafast charge transfer at the PbS quantum dot and phenyl-C61-butyric acid methyl ester interface

Handle URI:
http://hdl.handle.net/10754/563548
Title:
Quantum confinement-tunable ultrafast charge transfer at the PbS quantum dot and phenyl-C61-butyric acid methyl ester interface
Authors:
El-Ballouli, AlA'A O.; Alarousu, Erkki Antero; Bernardi, Marco; Aly, Shawkat Mohammede ( 0000-0002-0455-1892 ) ; Lagrow, Alec P.; Bakr, Osman M. ( 0000-0002-3428-1002 ) ; Mohammed, Omar F. ( 0000-0001-8500-1130 )
Abstract:
Quantum dot (QD) solar cells have emerged as promising low-cost alternatives to existing photovoltaic technologies. Here, we investigate charge transfer and separation at PbS QDs and phenyl-C61-butyric acid methyl ester (PCBM) interfaces using a combination of femtosecond broadband transient absorption (TA) spectroscopy and steady-state photoluminescence quenching measurements. We analyzed ultrafast electron injection and charge separation at PbS QD/PCBM interfaces for four different QD sizes and as a function of PCBM concentration. The results reveal that the energy band alignment, tuned by the quantum size effect, is the key element for efficient electron injection and charge separation processes. More specifically, the steady-state and time-resolved data demonstrate that only small-sized PbS QDs with a bandgap larger than 1 eV can transfer electrons to PCBM upon light absorption. We show that these trends result from the formation of a type-II interface band alignment, as a consequence of the size distribution of the QDs. Transient absorption data indicate that electron injection from photoexcited PbS QDs to PCBM occurs within our temporal resolution of 120 fs for QDs with bandgaps that achieve type-II alignment, while virtually all signals observed in smaller bandgap QD samples result from large bandgap outliers in the size distribution. Taken together, our results clearly demonstrate that charge transfer rates at QD interfaces can be tuned by several orders of magnitude by engineering the QD size distribution. The work presented here will advance both the design and the understanding of QD interfaces for solar energy conversion. © 2014 American Chemical Society.
KAUST Department:
Physical Sciences and Engineering (PSE) Division; Solar and Photovoltaic Engineering Research Center (SPERC); Materials Science and Engineering Program; Chemical Science Program; Functional Nanomaterials Lab (FuNL)
Publisher:
American Chemical Society (ACS)
Journal:
Journal of the American Chemical Society
Issue Date:
14-May-2014
DOI:
10.1021/ja413254g
Type:
Article
ISSN:
00027863
Sponsors:
Shawkat M. Aly is grateful for the post-doctoral fellowship provided by Saudi Basic Industries Corporation (SABIC). Cover design/illustration by Anastasia Khrenova.
Appears in Collections:
Articles; Physical Sciences and Engineering (PSE) Division; Chemical Science Program; Materials Science and Engineering Program; Solar and Photovoltaic Engineering Research Center (SPERC)

Full metadata record

DC FieldValue Language
dc.contributor.authorEl-Ballouli, AlA'A O.en
dc.contributor.authorAlarousu, Erkki Anteroen
dc.contributor.authorBernardi, Marcoen
dc.contributor.authorAly, Shawkat Mohammedeen
dc.contributor.authorLagrow, Alec P.en
dc.contributor.authorBakr, Osman M.en
dc.contributor.authorMohammed, Omar F.en
dc.date.accessioned2015-08-03T11:54:12Zen
dc.date.available2015-08-03T11:54:12Zen
dc.date.issued2014-05-14en
dc.identifier.issn00027863en
dc.identifier.doi10.1021/ja413254gen
dc.identifier.urihttp://hdl.handle.net/10754/563548en
dc.description.abstractQuantum dot (QD) solar cells have emerged as promising low-cost alternatives to existing photovoltaic technologies. Here, we investigate charge transfer and separation at PbS QDs and phenyl-C61-butyric acid methyl ester (PCBM) interfaces using a combination of femtosecond broadband transient absorption (TA) spectroscopy and steady-state photoluminescence quenching measurements. We analyzed ultrafast electron injection and charge separation at PbS QD/PCBM interfaces for four different QD sizes and as a function of PCBM concentration. The results reveal that the energy band alignment, tuned by the quantum size effect, is the key element for efficient electron injection and charge separation processes. More specifically, the steady-state and time-resolved data demonstrate that only small-sized PbS QDs with a bandgap larger than 1 eV can transfer electrons to PCBM upon light absorption. We show that these trends result from the formation of a type-II interface band alignment, as a consequence of the size distribution of the QDs. Transient absorption data indicate that electron injection from photoexcited PbS QDs to PCBM occurs within our temporal resolution of 120 fs for QDs with bandgaps that achieve type-II alignment, while virtually all signals observed in smaller bandgap QD samples result from large bandgap outliers in the size distribution. Taken together, our results clearly demonstrate that charge transfer rates at QD interfaces can be tuned by several orders of magnitude by engineering the QD size distribution. The work presented here will advance both the design and the understanding of QD interfaces for solar energy conversion. © 2014 American Chemical Society.en
dc.description.sponsorshipShawkat M. Aly is grateful for the post-doctoral fellowship provided by Saudi Basic Industries Corporation (SABIC). Cover design/illustration by Anastasia Khrenova.en
dc.publisherAmerican Chemical Society (ACS)en
dc.titleQuantum confinement-tunable ultrafast charge transfer at the PbS quantum dot and phenyl-C61-butyric acid methyl ester interfaceen
dc.typeArticleen
dc.contributor.departmentPhysical Sciences and Engineering (PSE) Divisionen
dc.contributor.departmentSolar and Photovoltaic Engineering Research Center (SPERC)en
dc.contributor.departmentMaterials Science and Engineering Programen
dc.contributor.departmentChemical Science Programen
dc.contributor.departmentFunctional Nanomaterials Lab (FuNL)en
dc.identifier.journalJournal of the American Chemical Societyen
dc.contributor.institutionDepartment of Physics, University of California at Berkeley, Berkeley, CA 94720-7300, United Statesen
kaust.authorAlarousu, Erkki Anteroen
kaust.authorAly, Shawkat Mohammedeen
kaust.authorBakr, Osman M.en
kaust.authorMohammed Abdelsaboor, Omar F.en
kaust.authorEl-Ballouli, AlA'A O.en
kaust.authorLagrow, Alec P.en
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