Variable Temperature Single‐Molecule Dynamics of MEH‐PPV

Lee, Young Jong; Kim, Doo Young; Grey, John K.; Barbara, Paul F.

doi:10.1002/cphc.200500300

Cited by 29 publications

(42 citation statements)

References 43 publications

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“…[29] Energy funneling to the HC sites from a broad range of absorbing chromophores in MEHPPV is a well-established hypothesis. [30] In addition, the presence of the HC phase provides better transport pathways for holes.…”

Section: Gupta Et Al/graded-bandgap Polymers For Photovoltaic Cellsmentioning

confidence: 99%

An Efficient Bulk‐Heterojunction Photovoltaic Cell Based on Energy Transfer in Graded‐Bandgap Polymers

Gupta

Kabra

Kolishetti

et al. 2006

Adv Funct Materials

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It is demonstrated that the energy transfer from low‐conjugated (LC) poly[2‐methoxy‐5‐(2‐ethylhexyloxy)‐1,4‐phenylene vinylene] (MEHPPV) to high‐conjugated (HC) MEHPPV, coupled with significant electron transfer from HC‐MEHPPV to an acceptor species, offers a viable route for an efficient photodiode over a wide spectral range. An enhanced incident‐photon‐to‐current conversion efficiency (IPCE) of 19 % over a wide spectral range and a power‐conversion efficiency (ηP) of 1 % (under monochromatic illumination at λ ∼ 530 nm and a power density of ca. 1 mW cm–2) are achieved in a ternary polymer‐blend film that consists of HC‐MEHPPV (low bandgap), LC‐MEHPPV (high bandgap), and an acceptor polymer, cyanoPPV (CNPPV), in an optimized ratio. The decisive role of the morphology that emerges during phase separation in the polymer blend is demonstrated by wide‐field photocurrent imaging.

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Section: Gupta Et Al/graded-bandgap Polymers For Photovoltaic Cellsmentioning

confidence: 99%

An Efficient Bulk‐Heterojunction Photovoltaic Cell Based on Energy Transfer in Graded‐Bandgap Polymers

Gupta

Kabra

Kolishetti

et al. 2006

Adv Funct Materials

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“…Gaining information about the lateral structure of the film from GISAXS [17][18][19] with the film density profile along the surface normal from X-ray reflectivity and the surface topography from AFM allows us to reconstruct the film morphology. We selected the well known and extensively studied photoactive homopolymers MEH-PPV [20,21] and P3HT [22][23][24] for this investigation and focus on the effect of the blending ratio on the film morphology. Except for the imperfect matching of the band-structures of these polymers this system can be a candidate in applications of organic electronics and photovoltaics.…”

Section: Introductionmentioning

confidence: 99%

Thin Films of Photoactive Polymer Blends

et al. 2009

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The morphology inside photoactive blended films of two conjugated homopolymers poly [(1-methoxy)-4-(2-ethylhexyloxy)-p-phenylene-vinylene] (MEH-PPV) and poly(3-hexylthiophene-2,5-diyl) (P3HT) is investigated. For both homopolymers a linear dependence of the installed film thickness from the concentration of the polymer solution used in spin coating is probed. This dependence allows preparation of an efficient series of blended films with constant thickness and different blending ratios. Information about the lateral structure inside the films is gained from grazing incidence small angle X-ray scattering. At the calculated critical blending ratio the smallest lateral separation between adjacent domains is found representing the highest surface contact between both homopolymers in the films. The presence of wetting layers at both interfaces as detected with X-ray reflectivity and atomic force microscopy is promising for photovoltaic applications. UV/Vis spectroscopy complements the structural investigation.

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“…The immobilization is typically achieved by embedding trace amounts of PPV in a polymer matrix such as polymethylmethacrylate (PMMA). This experimental procedure, however, suppresses torsional motions along the polymer backbone and may introduce artifacts arising from the steric hindrance (3,9,10).…”

mentioning

confidence: 99%

Unraveling electronic energy transfer in single conjugated polyelectrolytes encapsulated in lipid vesicles

Karam

Ngo²,

Rouiller³

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

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A method for the study of conjugated polyelectrolyte (CPE) photophysics in solution at the single-molecule level is described. Extended observation times of single polymer molecules are enabled by the encapsulation of the CPEs within 200-nm lipid vesicles, which are in turn immobilized on a surface. When combined with a molecular-level visualization of vesicles and CPE via cryo-transmission electron microscopy, these single-molecule spectroscopy studies on CPEs enable us to directly correlate the polymer conformation with its spectroscopic features. These studies are conducted with poly[5-methoxy-2-(3-sulfopropoxy)-1,4-phenylene-vinylene] (MPS-PPV, a negatively charged CPE), when encapsulated in neutral and in negatively charged lipid vesicles. MPS-PPV exists as a freely diffusing polymer when confined in negatively charged vesicles. Individual MPS-PPV molecules adopt a collapsed-chain conformation leading to efficient energy migration over multiple chromophores. Both the presence of stepwise photobleaching in fluorescence intensity-time trajectories and emission from low-energy chromophores along the chain are observed. These results correlate with the amplified sensing potential reported for MPS-PPV in aqueous solution. When confined within neutral vesicles, single MPS-PPV molecules adopt an extended conformation upon insertion in the lipid bilayer. In this case emission arises from multiple chromophores within the isolated polymer chains, leading to an exponential decay of the intensity over time and a broad blueshifted emission spectrum.lipid-polymer interaction | exciton migration | water-soluble light-emitting polymer | biosensing C urrent knowledge on how the interplay of polymer conformation and chromophore coupling affect energy transfer along a conjugated polymer backbone has been established following rigorous ensemble and single-molecule spectroscopy studies. Many of these studies involve polyphenylene vinylene (PPV)-based conjugated polymers decorated with alkyl side groups that facilitate their solubility in organic solvents. This knowledge is critical for developing conjugated polymer-based electroluminescent, photovoltaic, and sensor devices (1).The prevailing organization of a polymer backbone is expected to have direct effects on the coupling of neighboring chromophores (planar segments with delocalized π orbitals along the backbone) and on the energy transfer efficiency between these chromophores. Collapsed polymers, predominantly encountered in films prepared from poor solvents, exhibit long-range order where chains are found in close proximity, folded back on themselves (2, 3). Polymers will thus undergo efficient interchain or through-space energy transfer. On the contrary, polymers in solution are highly disordered, where the presence of defects along the chains together with freely accessible bond rotations should result in globular structures with larger intramolecular distances, on average. The predominant mode of energy transfer found in this case is through-bond or intramolecular ener...

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Variable Temperature Single‐Molecule Dynamics of MEH‐PPV

Cited by 29 publications

References 43 publications

An Efficient Bulk‐Heterojunction Photovoltaic Cell Based on Energy Transfer in Graded‐Bandgap Polymers

An Efficient Bulk‐Heterojunction Photovoltaic Cell Based on Energy Transfer in Graded‐Bandgap Polymers

Thin Films of Photoactive Polymer Blends

Unraveling electronic energy transfer in single conjugated polyelectrolytes encapsulated in lipid vesicles

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