Tuning the Optoelectronic Properties of Vinylene-Linked Donor−Acceptor Copolymers for Organic Photovoltaics

Handle URI:
http://hdl.handle.net/10754/599846
Title:
Tuning the Optoelectronic Properties of Vinylene-Linked Donor−Acceptor Copolymers for Organic Photovoltaics
Authors:
Ko, Sangwon; Mondal, Rajib; Risko, Chad; Lee, Jung Kyu; Hong, Sanghyun; McGehee, Michael D.; Brédas, Jean-Luc; Bao, Zhenan
Abstract:
Five new donor-acceptor copolymers containing the electron acceptor benzothiadiazole (BTZ) linked to the electron donors fluorene (FL) or cyclopentadithiophene (CPDT) via vinylene units were synthesized to study polymer structure-property relationships in organic photovoltaic devices. Both alternating (P) and random copolymers (P1-P4) were prepared via Suzuki and Stille polycondensations, respectively. The cyclopentadithiophene copolymers (P2 and P4) have smaller electrochemical band gaps (1.79 and 1.64 eV) compared to the fluorene-containing copolymers (2.08 and 1.95 eV for P1 and P3). However, the presence of CPDT raises the electrochemical HOMO energy levels (-4.83 and-4.91 eV for P2 and P4) compared to the FL copolymers (-5.06 and-5.15 eV for P1 and P3) leading to small open circuit voltages (Voc) in solar cells. The primary solution and thin-film UV-vis absorption peaks of P3 and P4, which do not contain alkylated thiophenes appended to the BTZ unit, are at lower energy and have larger absorption coefficients than their P1 and P2 counterparts. Detailed theoretical analyses of the geometric structure, electronic structure, and excited-state vertical transitions using density functional theory provide direct insight into the interplay between the structural modifications and resulting electronic and optical changes. A high molecular weight (Mn = 25 kg/mol) polymer with a large degree of polymerization (DPn = 21) was easily achieved for the random copolymer P1, leading to thin films with both a larger absorption coefficient and a larger hole mobility compared to the analogous alternating polymer P (Mn = 22 kg/mol, DPn = 18). An improved short circuit current and a power conversion efficiency up to 1.42% (Jsc = 5.82 mA/cm2, Voc = 0.765 V, and FF = 0.32) were achieved in bulk heterojunction solar cells based on P1. © 2010 American Chemical Society.
Citation:
Ko S, Mondal R, Risko C, Lee JK, Hong S, et al. (2010) Tuning the Optoelectronic Properties of Vinylene-Linked Donor−Acceptor Copolymers for Organic Photovoltaics. Macromolecules 43: 6685–6698. Available: http://dx.doi.org/10.1021/ma101088f.
Publisher:
American Chemical Society (ACS)
Journal:
Macromolecules
KAUST Grant Number:
KUS-C1-015-21
Issue Date:
24-Aug-2010
DOI:
10.1021/ma101088f
Type:
Article
ISSN:
0024-9297; 1520-5835
Sponsors:
This publication was partially based on work supported by the Center for Advanced Molecular Photo-voltaics, Award No KUS-C1-015-21, made by King Abdullah University of Science and Technology (KAUST). We also acknowledge support from the Global Climate and Energy Program (GCEP) and the Stanford Center for Polymer Interfaces and Macromolecular Assemblies (CPIMA). We thank Prof. Alan Sellinger, Eric Verploegen, Hector A. Becerril, and George Y. Margulis for helpful discussions.
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Publications Acknowledging KAUST Support

Full metadata record

DC FieldValue Language
dc.contributor.authorKo, Sangwonen
dc.contributor.authorMondal, Rajiben
dc.contributor.authorRisko, Chaden
dc.contributor.authorLee, Jung Kyuen
dc.contributor.authorHong, Sanghyunen
dc.contributor.authorMcGehee, Michael D.en
dc.contributor.authorBrédas, Jean-Lucen
dc.contributor.authorBao, Zhenanen
dc.date.accessioned2016-02-28T06:42:46Zen
dc.date.available2016-02-28T06:42:46Zen
dc.date.issued2010-08-24en
dc.identifier.citationKo S, Mondal R, Risko C, Lee JK, Hong S, et al. (2010) Tuning the Optoelectronic Properties of Vinylene-Linked Donor−Acceptor Copolymers for Organic Photovoltaics. Macromolecules 43: 6685–6698. Available: http://dx.doi.org/10.1021/ma101088f.en
dc.identifier.issn0024-9297en
dc.identifier.issn1520-5835en
dc.identifier.doi10.1021/ma101088fen
dc.identifier.urihttp://hdl.handle.net/10754/599846en
dc.description.abstractFive new donor-acceptor copolymers containing the electron acceptor benzothiadiazole (BTZ) linked to the electron donors fluorene (FL) or cyclopentadithiophene (CPDT) via vinylene units were synthesized to study polymer structure-property relationships in organic photovoltaic devices. Both alternating (P) and random copolymers (P1-P4) were prepared via Suzuki and Stille polycondensations, respectively. The cyclopentadithiophene copolymers (P2 and P4) have smaller electrochemical band gaps (1.79 and 1.64 eV) compared to the fluorene-containing copolymers (2.08 and 1.95 eV for P1 and P3). However, the presence of CPDT raises the electrochemical HOMO energy levels (-4.83 and-4.91 eV for P2 and P4) compared to the FL copolymers (-5.06 and-5.15 eV for P1 and P3) leading to small open circuit voltages (Voc) in solar cells. The primary solution and thin-film UV-vis absorption peaks of P3 and P4, which do not contain alkylated thiophenes appended to the BTZ unit, are at lower energy and have larger absorption coefficients than their P1 and P2 counterparts. Detailed theoretical analyses of the geometric structure, electronic structure, and excited-state vertical transitions using density functional theory provide direct insight into the interplay between the structural modifications and resulting electronic and optical changes. A high molecular weight (Mn = 25 kg/mol) polymer with a large degree of polymerization (DPn = 21) was easily achieved for the random copolymer P1, leading to thin films with both a larger absorption coefficient and a larger hole mobility compared to the analogous alternating polymer P (Mn = 22 kg/mol, DPn = 18). An improved short circuit current and a power conversion efficiency up to 1.42% (Jsc = 5.82 mA/cm2, Voc = 0.765 V, and FF = 0.32) were achieved in bulk heterojunction solar cells based on P1. © 2010 American Chemical Society.en
dc.description.sponsorshipThis publication was partially based on work supported by the Center for Advanced Molecular Photo-voltaics, Award No KUS-C1-015-21, made by King Abdullah University of Science and Technology (KAUST). We also acknowledge support from the Global Climate and Energy Program (GCEP) and the Stanford Center for Polymer Interfaces and Macromolecular Assemblies (CPIMA). We thank Prof. Alan Sellinger, Eric Verploegen, Hector A. Becerril, and George Y. Margulis for helpful discussions.en
dc.publisherAmerican Chemical Society (ACS)en
dc.titleTuning the Optoelectronic Properties of Vinylene-Linked Donor−Acceptor Copolymers for Organic Photovoltaicsen
dc.typeArticleen
dc.identifier.journalMacromoleculesen
dc.contributor.institutionStanford University, Palo Alto, United Statesen
dc.contributor.institutionGeorgia Institute of Technology, Atlanta, United Statesen
kaust.grant.numberKUS-C1-015-21en
kaust.grant.fundedcenterCenter for Advanced Molecular Photovoltaics (CAMP)en
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