Molecular-Scale and Nanoscale Morphology of P3HT:PCBM Bulk Heterojunctions: Energy-Filtered TEM and Low-Dose HREM

Drummy, Lawrence F.; Davis, R. J.; Moore, Diana L.; Durstock, Michael F.; Vaia, Richard A.; Hsu, Julia W. P.

doi:10.1021/cm102463t

Cited by 130 publications

(149 citation statements)

References 36 publications

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“…The 22±4 eV image utilized the plasmon peak of the p-type organic semiconductor to enhance the contrast in the electron energy loss spectra, and the thickness map is obtained from the ratio of unfiltered and filtered image, yielding pixel by pixel values of t/l, where t is film thickness in nanometre and l is the electron mean free pathway. Both the 22 ± 4 eV image and the thickness map suggest that there is indeed an additional layer underneath C8-BTBT 39,40 . Further indication of vertical phase separation in the C8-BTBT:PS film was observed by scanning electron microscopy using a thicker film with a higher percentage of PS, showing a similar phase-separated structure, where the PS layer was sandwiched between the C8-BTBT and PVP film (Fig.…”

Section: Discussionmentioning

confidence: 92%

Ultra-high mobility transparent organic thin film transistors grown by an off-centre spin-coating method

et al. 2014

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Organic semiconductors with higher carrier mobility and better transparency have been actively pursued for numerous applications, such as flat-panel display backplane and sensor arrays. The carrier mobility is an important figure of merit and is sensitively influenced by the crystallinity and the molecular arrangement in a crystal lattice. Here we describe the growth of a highly aligned meta-stable structure of 2,7-dioctyl[1]benzothieno [3,2-b][1]benzothiophene (C8-BTBT) from a blended solution of C8-BTBT and polystyrene by using a novel offcentre spin-coating method. Combined with a vertical phase separation of the blend, the highly aligned, meta-stable C8-BTBT films provide a significantly increased thin film transistor hole mobility up to 43 cm 2 Vs À 1 (25 cm 2 Vs À 1 on average), which is the highest value reported to date for all organic molecules. The resulting transistors show high transparency of 490% over the visible spectrum, indicating their potential for transparent, high-performance organic electronics.

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Section: Discussionmentioning

confidence: 92%

Ultra-high mobility transparent organic thin film transistors grown by an off-centre spin-coating method

et al. 2014

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“…3b. Note that the energy window is centred at 19 ± 4 eV to provide maximum contrast for P3HT, and as a result, the bright regions in the micrographs correspond to P3HT-rich domains 33 . It was observed that the P3HT and SD-P3HT domains overlap with each other over the whole film, indicating the formation of an interpenetrating network with no visible isolated P3HT fibrils.…”

Section: Resultsmentioning

confidence: 99%

The isotopic effects of deuteration on optoelectronic properties of conducting polymers

et al. 2014

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The attractive optoelectronic properties of conducting polymers depend sensitively upon intra-and inter-polymer chain interactions, and therefore new methods to manipulate these interactions are continually being pursued. Here, we report a study of the isotopic effects of deuterium substitution on the structure, morphology and optoelectronic properties of regioregular poly(3-hexylthiophene)s with an approach that combines the synthesis of deuterated materials, optoelectronic properties measurements, theoretical simulation and neutron scattering. Selective substitutions of deuterium on the backbone or side-chains of poly(3-hexylthiophene)s result in distinct optoelectronic responses in poly(3-hexylthiophene)/[6,6]-phenyl-C61-butyric acid methyl ester (PCBM) photovoltaics. Specifically, the weak non-covalent intermolecular interactions induced by the main-chain deuteration are shown to change the film crystallinity and morphology of the active layer, consequently reducing the short-circuit current. However, side-chain deuteration does not significantly modify the film morphology but causes a decreased electronic coupling, the formation of a charge transfer state, and increased electron-phonon coupling, leading to a remarkable reduction in the open circuit voltage.

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“…Similar structures have been observed previously with TEM in P3HT domains inside P3HT:PCBM blends. [ 40 ] …”

Section: Transmission Electron Microscopy (Tem)mentioning

confidence: 99%

The Role of Photon Energy in Free Charge Generation in Bulk Heterojunction Solar Cells

Nuzzo

Koster

Gevaerts

et al. 2014

Advanced Energy Materials

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To determine the role of photon energy on charge generation in bulk heterojunction solar cells, the bias voltage dependence of photocurrent for excitation with photon energies below and above the optical band gap is investigated in two structurally related polymer solar cells. Charges generated in (poly[2,6‐(4,4‐bis(2‐ethylhexyl)‐4H‐cyclopenta[2,1‐b;3,4‐b′′]dithiophene)‐alt‐4,7‐(2,1,3‐benzothiadiazole)] (C‐PCPDTBT):[6,6]‐phenyl‐C61‐butyric acid methyl ester (PCBM) solar cells via excitation of the low‐energy charge transfer (CT) state, situated below the optical band gap, need more voltage to be extracted than charges generated with excitation above the optical band gap. This indicates a lower effective binding energy of the photogenerated electrons and holes when the excitation is above the optical band gap than when excitation is to the bottom of the CT state. In blends of PCBM with the silicon‐analogue, poly[(4,4‐bis(2‐ethylhexyl)dithieno[3,2‐b:2′,3′‐d]silole)‐2,6‐diyl‐alt‐(2,1,3‐benzothiadiazole)‐4,7‐diyl] (Si‐PCPDTBT), there is no effect of the photon energy on the electric field dependence of the dissociation efficiency of the CT state. C‐PCPDTBT and Si‐PCPDTBT have very similar electronic properties, but their blends with PCBM differ in the nanoscale phase separation. The morphology is coarser and more crystalline in Si‐PCPDTBT:PCBM blends. The results demonstrate that the nanomorphological properties of the bulk heterojunction are important for determining the effective binding energy in the generation of free charges at the heterojunction.

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Molecular-Scale and Nanoscale Morphology of P3HT:PCBM Bulk Heterojunctions: Energy-Filtered TEM and Low-Dose HREM

Cited by 130 publications

References 36 publications

Ultra-high mobility transparent organic thin film transistors grown by an off-centre spin-coating method

Ultra-high mobility transparent organic thin film transistors grown by an off-centre spin-coating method

The isotopic effects of deuteration on optoelectronic properties of conducting polymers

The Role of Photon Energy in Free Charge Generation in Bulk Heterojunction Solar Cells

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