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dc.contributor.authorLombeck, Fen
dc.contributor.authorKomber, Hen
dc.contributor.authorFazzi, Den
dc.contributor.authorNava, Den
dc.contributor.authorKuhlmann, Jen
dc.contributor.authorStegerer, Den
dc.contributor.authorStrassel, Ken
dc.contributor.authorBrandt, Jen
dc.contributor.authorde Zerio Mendaza, ADen
dc.contributor.authorMüller, Cen
dc.contributor.authorThiel, Wen
dc.contributor.authorCaironi, Men
dc.contributor.authorFriend, Richarden
dc.contributor.authorSommer, Men
dc.date.accessioned2017-05-03T15:36:36Z
dc.date.available2017-05-03T15:36:36Z
dc.date.issued2016-11-09en
dc.identifier.issn1614-6832
dc.identifier.urihttps://www.repository.cam.ac.uk/handle/1810/264010
dc.description.abstractThe photophysical properties and solar cell performance of the classical donor–acceptor copolymer PCDTBT (poly($\textit{N}$-9′-heptadecanyl-2,7-carbazole-$\textit{alt}$ -5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole))) in relation to unintentionally formed main chain defects are investigated. Carbazole–carbazole homocouplings (Cbz hc) are found to significant extent in PCDTBT made with a variety of Suzuki polycondensation conditions. Cbz hc vary between 0 and 8 mol% depending on the synthetic protocol used, and are quantified by detailed nuclear magnetic resonance spectroscopy including model compounds, which allows to establish a calibration curve from optical spectroscopy. The results are corroborated by extended time-dependent density functional theory investigations on the structural, electronic, and optical properties of regularly alternating and homocoupled chains. The photovoltaic properties of PCDTBT:fullerene blend solar cells significantly depend on the Cbz hc content for constant molecular weight, whereby an increasing amount of Cbz hc leads to strongly decreased short circuit currents J$_{sc}$. With increasing Cbz hc content, J$_{sc}$decreases more strongly than the intensity of the low energy absorption band, suggesting that small losses in absorption cannot explain the decrease in J$_{sc}$ alone, rather than combined effects of a more localized LUMO level on the TBT unit and lower hole mobilities found in highly defective samples. Homocoupling-free PCDTBT with optimized molecular weight yields the highest efficiency up to 7.2% without extensive optimization.
dc.description.sponsorshipF.L., M.S., and R.F. gratefully acknowledge the EPSRC for funding. M.S. thanks the University of Freiburg (Innovationsfond Forschung) and the DFG for funding (SPP 1355). D.F. acknowledges the Alexander von Humboldt foundation for a postdoctoral research fellowship. A.D.Z.M. and C.M. thank the Swedish Research Council for funding.
dc.languageengen
dc.language.isoenen
dc.publisherWiley
dc.subjectconjugated polymersen
dc.subjecthomocoupling defectsen
dc.subjectPCDTBTen
dc.subjectorganice solar cellsen
dc.subjectSuzuki polycondensationen
dc.titleOn the Effect of Prevalent Carbazole Homocoupling Defects on the Photovoltaic Performance of PCDTBT:PC$_{17}$BM Solar Cellsen
dc.typeArticle
prism.issueIdentifier21en
prism.number1601232en
prism.publicationDate2016en
prism.publicationNameAdvanced Energy Materialsen
prism.volume6en
dc.identifier.doi10.17863/CAM.9371
dcterms.dateAccepted2016-06-24en
rioxxterms.versionofrecord10.1002/aenm.201601232en
rioxxterms.versionAMen
rioxxterms.licenseref.urihttp://www.rioxx.net/licenses/all-rights-reserveden
rioxxterms.licenseref.startdate2016-11-09en
dc.contributor.orcidFriend, Richard [0000-0001-6565-6308]
dc.identifier.eissn1614-6840
rioxxterms.typeJournal Article/Reviewen
pubs.funder-project-idEPSRC (EP/G060738/1)
cam.issuedOnline2016-08-08en
rioxxterms.freetoread.startdate2017-11-09


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