Charge Separation in Intermixed Polymer:PC70BM Photovoltaic Blends: Correlating Structural and Photophysical Length Scales as a Function of Blend Composition

Handle URI:
http://hdl.handle.net/10754/625579
Title:
Charge Separation in Intermixed Polymer:PC70BM Photovoltaic Blends: Correlating Structural and Photophysical Length Scales as a Function of Blend Composition
Authors:
Utzat, Hendrik; Dimitrov, Stoichko D. ( 0000-0002-1564-7080 ) ; Wheeler, Scot ( 0000-0001-7335-5919 ) ; Collado-Fregoso, Elisa; Tuladhar, Pabitra Shakya; Schroeder, Bob C. ( 0000-0002-9793-631X ) ; McCulloch, Iain ( 0000-0002-6340-7217 ) ; Durrant, James R. ( 0000-0001-8353-7345 )
Abstract:
A key challenge in achieving control over photocurrent generation by bulk-heterojunction organic solar cells is understanding how the morphology of the active layer impacts charge separation and in particular the separation dynamics within molecularly intermixed donor-acceptor domains versus the dynamics between phase-segregated domains. This paper addresses this issue by studying blends and devices of the amorphous silicon-indacenodithiophene polymer SiIDT-DTBT and the acceptor PCBM. By changing the blend composition, we modulate the size and density of the pure and intermixed domains on the nanometer length scale. Laser spectroscopic studies show that these changes in morphology correlate quantitatively with the changes in charge separation dynamics on the nanosecond time scale and with device photocurrent densities. At low fullerene compositions, where only a single, molecularly intermixed polymer-fullerene phase is observed, photoexcitation results in a ∼ 30% charge loss from geminate polaron pair recombination, which is further studied via light intensity experiments showing that the radius of the polaron pairs in the intermixed phase is 3-5 nm. At high fullerene compositions (≥67%), where the intermixed domains are 1-3 nm and the pure fullerene phases reach ∼4 nm, the geminate recombination is suppressed by the reduction of the intermixed phase, making the fullerene domains accessible for electron escape.
KAUST Department:
KAUST Solar Center (KSC); Physical Sciences and Engineering (PSE) Division
Citation:
Utzat H, Dimitrov SD, Wheeler S, Collado-Fregoso E, Tuladhar PS, et al. (2017) Charge Separation in Intermixed Polymer:PC70BM Photovoltaic Blends: Correlating Structural and Photophysical Length Scales as a Function of Blend Composition. The Journal of Physical Chemistry C 121: 9790–9801. Available: http://dx.doi.org/10.1021/acs.jpcc.7b02898.
Publisher:
American Chemical Society (ACS)
Journal:
The Journal of Physical Chemistry C
Issue Date:
24-Apr-2017
DOI:
10.1021/acs.jpcc.7b02898
Type:
Article
ISSN:
1932-7447; 1932-7455
Sponsors:
The authors thank Florent Deledalle for the helpful discussions of nongeminate recombination dynamics and Safa Shoaee for measuring TEM images. We also thank the EPSRC (EP/IO1927B/1 and EP/K011987/1) for funding. B.C.S. acknowledges the National Research Fund of Luxembourg for financial support. This work is partially funded by the European regional Development Fund through the Welsh Government.
Additional Links:
http://pubs.acs.org/doi/full/10.1021/acs.jpcc.7b02898
Appears in Collections:
Articles; Physical Sciences and Engineering (PSE) Division; Solar and Photovoltaic Engineering Research Center (SPERC)

Full metadata record

DC FieldValue Language
dc.contributor.authorUtzat, Hendriken
dc.contributor.authorDimitrov, Stoichko D.en
dc.contributor.authorWheeler, Scoten
dc.contributor.authorCollado-Fregoso, Elisaen
dc.contributor.authorTuladhar, Pabitra Shakyaen
dc.contributor.authorSchroeder, Bob C.en
dc.contributor.authorMcCulloch, Iainen
dc.contributor.authorDurrant, James R.en
dc.date.accessioned2017-10-03T12:49:27Z-
dc.date.available2017-10-03T12:49:27Z-
dc.date.issued2017-04-24en
dc.identifier.citationUtzat H, Dimitrov SD, Wheeler S, Collado-Fregoso E, Tuladhar PS, et al. (2017) Charge Separation in Intermixed Polymer:PC70BM Photovoltaic Blends: Correlating Structural and Photophysical Length Scales as a Function of Blend Composition. The Journal of Physical Chemistry C 121: 9790–9801. Available: http://dx.doi.org/10.1021/acs.jpcc.7b02898.en
dc.identifier.issn1932-7447en
dc.identifier.issn1932-7455en
dc.identifier.doi10.1021/acs.jpcc.7b02898en
dc.identifier.urihttp://hdl.handle.net/10754/625579-
dc.description.abstractA key challenge in achieving control over photocurrent generation by bulk-heterojunction organic solar cells is understanding how the morphology of the active layer impacts charge separation and in particular the separation dynamics within molecularly intermixed donor-acceptor domains versus the dynamics between phase-segregated domains. This paper addresses this issue by studying blends and devices of the amorphous silicon-indacenodithiophene polymer SiIDT-DTBT and the acceptor PCBM. By changing the blend composition, we modulate the size and density of the pure and intermixed domains on the nanometer length scale. Laser spectroscopic studies show that these changes in morphology correlate quantitatively with the changes in charge separation dynamics on the nanosecond time scale and with device photocurrent densities. At low fullerene compositions, where only a single, molecularly intermixed polymer-fullerene phase is observed, photoexcitation results in a ∼ 30% charge loss from geminate polaron pair recombination, which is further studied via light intensity experiments showing that the radius of the polaron pairs in the intermixed phase is 3-5 nm. At high fullerene compositions (≥67%), where the intermixed domains are 1-3 nm and the pure fullerene phases reach ∼4 nm, the geminate recombination is suppressed by the reduction of the intermixed phase, making the fullerene domains accessible for electron escape.en
dc.description.sponsorshipThe authors thank Florent Deledalle for the helpful discussions of nongeminate recombination dynamics and Safa Shoaee for measuring TEM images. We also thank the EPSRC (EP/IO1927B/1 and EP/K011987/1) for funding. B.C.S. acknowledges the National Research Fund of Luxembourg for financial support. This work is partially funded by the European regional Development Fund through the Welsh Government.en
dc.publisherAmerican Chemical Society (ACS)en
dc.relation.urlhttp://pubs.acs.org/doi/full/10.1021/acs.jpcc.7b02898en
dc.titleCharge Separation in Intermixed Polymer:PC70BM Photovoltaic Blends: Correlating Structural and Photophysical Length Scales as a Function of Blend Compositionen
dc.typeArticleen
dc.contributor.departmentKAUST Solar Center (KSC)en
dc.contributor.departmentPhysical Sciences and Engineering (PSE) Divisionen
dc.identifier.journalThe Journal of Physical Chemistry Cen
dc.contributor.institutionDepartment of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA, 02139, , United Statesen
dc.contributor.institutionCentre for Plastic Electronics, Department of Chemistry, Imperial College London, Exhibition Road, London, SW7 2AZ, , United Kingdomen
dc.contributor.institutionSPECIFIC, College of Engineering, Swansea University, Bay Campus, Swansea, SA1 8EN, , United Kingdomen
dc.contributor.institutionMaterials Research Institute, School of Biological and Chemical Sciences, Queen Mary University London, London, , , United Kingdomen
dc.contributor.institutionDepartment of Chemical Engineering, Stanford University, 443 Via Ortega, Stanford, CA, 94305, , United Statesen
kaust.authorMcCulloch, Iainen
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