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Title
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Spin-dependent photophysics in polymers lightly doped with fullerene derivatives : photoluminescence and electrically detected magnetic resonance
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Author
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Abstract
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| Lightly fullerene-doped polymers are suitable composite systems to study spin-dependent bimolecular interactions among charge excitations due to their long lifetimes in these systems. These interactions can affect the photocurrent as well as the open-circuit voltage in an organic solar cell. Combining photoluminescence detected magnetic resonance (PLDMR) and electrically detected magnetic resonance (EDMR) spectroscopies we study films and devices of poly(p-phenylene vinylene) polymers poly[2-methoxy-5-(3',7'-dimethyloctyloxy)-1,4-phenylene vinylene] (MDMO-PPV) and superyellow PPV (SY-PPV) lightly doped with various fullerene derivatives [6,6]-phenyl C-61 butyric acid methyl ester (PCBM), bis[60]PCBM (bis-PCBM), indene-C-60 bisadduct (ICBA), and [6,6]-phenyl C-71 butyric acid methyl ester (PC70BM). (i) We demonstrate strong fullerene triplet exciton (TE) production in SY-PPV: fullerene blends, whereas this is absent in MDMO-PPV:PCBM and only very weak in MDMO-PPV:ICBA. The low TE production in blends with MDMO-PPV is attributed to a weaker singlet-singlet energy-transfer coupling and an unfavorable triplet level alignment between the blend components. (ii) The fullerene TE spectra are analyzed on the basis of a single type of triplet excitation in PCBM, bis-PCBM, and ICBA, and two triplet species in PC70BM which are attributed to the alpha- and beta-type isomers of the latter molecule. (iii) The sign change with increasing temperature of the g similar to 2 sharp central line in photo-EDMR, which is observed both in pristine SY-PPV and in blends with fullerene, is correlated to a transition from dominant TE-polaron annihilation to nongeminate polaron recombination processes. |
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Language
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English
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Source (journal)
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Physical review : B : condensed matter and materials physics. - Lancaster, Pa, 1998 - 2015
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Publication
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Lancaster, Pa
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2015
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ISSN
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1098-0121
[print]
1550-235X
[online]
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DOI
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10.1103/PHYSREVB.91.085309
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Volume/pages
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91
:8
(2015)
, 11 p.
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Article Reference
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085309
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ISI
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000351775500005
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Medium
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E-only publicatie
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Full text (Publisher's DOI)
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Full text (open access)
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