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dc.contributor.authorKim, Do Hwan
dc.contributor.authorAyzner, Alexander L.
dc.contributor.authorAppleton, Anthony L.
dc.contributor.authorSchmidt, Kristin
dc.contributor.authorMei, Jianguo
dc.contributor.authorToney, Michael F.
dc.contributor.authorBao, Zhenan
dc.date.accessioned2016-02-25T12:57:11Z
dc.date.available2016-02-25T12:57:11Z
dc.date.issued2013-02-12
dc.identifier.citationKim DH, Ayzner AL, Appleton AL, Schmidt K, Mei J, et al. (2013) Comparison of the Photovoltaic Characteristics and Nanostructure of Fullerenes Blended with Conjugated Polymers with Siloxane-Terminated and Branched Aliphatic Side Chains. Chem Mater 25: 431–440. Available: http://dx.doi.org/10.1021/cm303572d.
dc.identifier.issn0897-4756
dc.identifier.issn1520-5002
dc.identifier.doi10.1021/cm303572d
dc.identifier.urihttp://hdl.handle.net/10754/597815
dc.description.abstractAll-organic bulk heterojunction solar cells based on blends of conjugated polymers with fullerenes have recently surpassed the 8% efficiency mark and are well on their way to the industrially relevant ∼15% threshold. Using a low band-gap conjugated polymer, we have recently shown that polymer side chain engineering can lead to dramatic improvement in the in-plane charge carrier mobility. In this article, we investigate the effectiveness of siloxy side chain derivatization in controlling the photovoltaic performance of polymer:[6,6]-phenyl-C[71]-butyric acid methyl ester (PC71BM) blends and hence its influence on charge transport in the out-of-plane direction relevant for organic solar cells. We find that, in neat blends, the photocurrent of the polymer with siloxy side chains (PII2T-Si) is 4 times greater than that in blends using the polymer with branched aliphatic side chains (PII2T-ref). This difference is due to a larger out-of-plane hole mobility for PII2T-Si brought about by a largely face-on crystallite orientation as well as more optimal nanoscale polymer:PC71BM mixing. However, upon incorporating a common processing additive, 1,8-diiodooctane (DIO), into the spin-casting blend solution and following optimization, the PII2T-ref:PC71BM OPV device performance undergoes a large improvement and becomes the better-performing device, almost independent of DIO concentration (>1%). We find that the precise amount of DIO plays a larger role in determining the efficiency of PII2T-Si:PC71BM, and even at its maximum, the device performance lags behind optimized PII2T-ref:PC71BM blends. Using a combination of atomic force microscopy and small- and wide-angle X-ray scattering, we are able to elucidate the morphological modifications associated with the DIO-induced changes in both the nanoscale morphology and the molecular packing in blend films. © 2012 American Chemical Society.
dc.description.sponsorshipThis work was partially supported by the Center for Advanced Molecular Photovoltaics, award no. KUS-C1-015-21, made by King Abdullah University of Science and Technology. We also acknowledge support from the Global Climate and Energy Program at Stanford and the Camille and Henry Dreyfus Postdoctoral Program in Environmental Chemistry. GIXD measurements were carried out at the Stanford Synchrotron Radiation Laboratory, a national user facility operated by Stanford University on behalf of the U.S. Department of Energy, Office of Basic Energy Sciences.
dc.publisherAmerican Chemical Society (ACS)
dc.subjectDIO
dc.subjectmolecular packing
dc.subjectorganic photovoltaics
dc.subjectsiloxane side chain
dc.subjectthin-film morphology
dc.subjectX-ray scattering
dc.titleComparison of the Photovoltaic Characteristics and Nanostructure of Fullerenes Blended with Conjugated Polymers with Siloxane-Terminated and Branched Aliphatic Side Chains
dc.typeArticle
dc.identifier.journalChemistry of Materials
dc.contributor.institutionStanford University, Palo Alto, United States
dc.contributor.institutionStanford Synchrotron Radiation Laboratory, Menlo Park, United States
dc.contributor.institutionSoongsil University, Seoul, South Korea
kaust.grant.numberKUS-C1-015-21
kaust.grant.fundedcenterCenter for Advanced Molecular Photovoltaics (CAMP)


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