Preparation and Characterization of Fulleroid and Methanofullerene Derivatives

Hummelen, Jan C.; Knight, Brian; LePeq, F.; Wudl, Fred; Yao, Jie; Wilkins, Charles L.

doi:10.1021/jo00108a012

Cited by 1,224 publications

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“…[41][42][43] 1-(3-Methoxycarbonyl)propyl-1-phenyl-[6,6]C 61 (PCBM) was kindly supplied from the University of Groningen and used as received. 46 To the polythiophene and PCBM added chlorobenzene (Aldrich) at a concentration of ~ 10 mg mL −1 . For P(T 12 T 12 TT 0 ), P(T 0 T 0 TT 16 ), P(T 0 TT 16 ), and P(T 12 SeT 12 ), the solution was heated in a water bath at 100 °C for a few minutes to be dissolved homogeneously.…”

Section: Methodsmentioning

confidence: 99%

Charge Carrier Formation in Polythiophene/Fullerene Blend Films Studied by Transient Absorption Spectroscopy

et al. 2008

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Abstract:We report herein a comparison of the photophysics of a series of polythiophenes with ionization potentials ranging from 4.8 to 5.6 eV as pristine films and when blended with 5 wt% 1-(3-methoxycarbonyl)propyl-1-phenyl-[6,6]C 61 (PCBM). Three polymers are observed to give amorphous films, attributed to a non-planar geometry of their backbone whilst the other five polymers, including poly(3-hexylthiophene), give more crystalline films. Optical excitation of the pristine films of the amorphous polymers is observed by transient absorption spectroscopy to give rise to polymer triplet formation. For the more crystalline pristine polymers, no triplet formation is observed, but rather a short-lived (~ 100 ns), broad photoinduced absorption feature assigned to polymer polarons. For all polymers, the addition of 5 wt% PCBM resulted in 70 -90% quenching of polymer photoluminescence (PL), indicative of efficient quenching of polythiophene excitons. Remarkably, despite this efficient exciton quenching, the yield of dissociated polymer + and PCBM − polarons, assayed by the appearance of a long-lived, powerlaw decay phase assigned to bimolecular recombination of these polarons, was observed to vary by over two orders of magnitude depending upon the polymer employed. In addition to this power-law decay phase, the blend films exhibited short-lived decays assigned, for the amorphous polymers, to neutral triplet states generated by geminate recombination of bound radical pairs and, for the more crystalline polymers, to the direct observation of the geminate recombination of these bound radical pairs to ground. These observations are discussed in terms of a two-step kinetic model for charge generation in polythiophene/PCBM blend films analogous to that reported to explain the observation of exciplex-like emission in poly(p-phenylenevinylene)-based blend films. Remarkably, we find a excellent correlation between the free energy difference for charge separation (ΔG CS rel ) and yield of the long-lived charge generation yield, with efficient charge generation requiring a much larger ΔG CS rel than that required to achieve efficient PL 3 quenching. We suggest this observation is consistent with a model where the excess thermal energy of the initially formed polarons pairs is necessary to overcome their coulomb binding energy. This observation has important implications for synthetic strategies to optimize organic solar cell performance, as it implies that, at least devices based on polythiophene/PCBM blend films, a large ΔG CS rel (or LUMO level offset) is required to achieve efficient charge dissociation.4

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Section: Methodsmentioning

confidence: 99%

Charge Carrier Formation in Polythiophene/Fullerene Blend Films Studied by Transient Absorption Spectroscopy

et al. 2008

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“…In addition some data were taken from the literature. The materials are the following: P3HT, poly(3-hexylthiophene); 14 PCDTBT, poly[carbazoledithienyl-benzothiadiazole); 15,16 PTB7, poly(thieno [3,4- 21 PC 60(70) BM, phenyl-C 61(70) -butyric acid methyl ester; 22 and ICBA, indene-C 60 bisadduct…”

Section: Background and Measurement Methodologymentioning

confidence: 99%

Electronic Structure and Transition Energies in Polymer–Fullerene Bulk Heterojunctions

et al. 2014

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Photocurrent spectroscopy is used to measure both the charge transfer and exciton optical absorption spectra of various bulk heterojunction organic solar cells. The energy difference between the polymer HOMO energy and the fullerene LUMO energy is obtained from the spectra, along with the disorder energy. Combining information from cells with several different polymers and fullerenes allows measurements of the energy differences between HOMO or LUMO energies for about 10 different polymers and fullerenes, with an estimated uncertainty of 50 meV. Heterojunction band offsets are obtained for the various cells, distinguishing between the excitonic and the single-carrier band offsets. The cell open-circuit voltage is shown to be closely correlated with the interface band gap. The exciton disorder energy is directly correlated to the band-tail disorder and we also consider the effects of exciton thermalization on the charge generation mechanism. The data indicate that an energy offset between the polymer exciton and the charge transfer ground state below about 0.25 eV adversely affects the cell performance, while a HOMO band offset below about 0.2−0.3 eV also degrades cell performance but by a different mechanism.

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“…% of the highly soluble C 60 derivative [6,6]phenyl-C61-butyric acid-methyl ester (PCBM) [15] (material 1) or, without a sensitizer, (material 2). Material 3 was produced by adding a very small amount of the oxidizing agent tri-(4-bromphenyl)-aminium hexachloroantimonate (TBPAH; Aldrich) to 1 as a redox dopant, which is commonly used in the area of organic light-emitting diodes (OLEDs).…”

Section: Methodsmentioning

confidence: 99%

Photophysical and Redox NIR‐Sensitivity Enhancement in Photorefractive Polymer Composites

et al. 2004

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Preparation and Characterization of Fulleroid and Methanofullerene Derivatives

Cited by 1,224 publications

References 0 publications

Charge Carrier Formation in Polythiophene/Fullerene Blend Films Studied by Transient Absorption Spectroscopy

Charge Carrier Formation in Polythiophene/Fullerene Blend Films Studied by Transient Absorption Spectroscopy

Electronic Structure and Transition Energies in Polymer–Fullerene Bulk Heterojunctions

Photophysical and Redox NIR‐Sensitivity Enhancement in Photorefractive Polymer Composites

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