| 1. |
- Aasmundtveit, K.E., et al.
(författare)
-
Structural ordering in phenyl-substituted polythiophenes
- 2000
-
Ingår i: Macromolecules. - : American Chemical Society (ACS). - 0024-9297 .- 1520-5835. ; 33:15, s. 5481-5489
-
Tidskriftsartikel (refereegranskat)abstract
- Various substituted poly(phenylthiophene)s have been studied by X-ray diffraction. They are semicrystalline, with very different degrees of crystallinity. Those with para-substituted phenyl groups have a low degree of crystallinity, whereas those with ortho-substituted phenyl groups are more crystalline. The most crystalline materials in this study have two equally long substituents on the phenyl ring, one at the ortho position and the other at the ortho or meta position on the opposite side of the phenyl ring. Poly(3-(2,5-dioctylphenyl)thiophene) (PDOPT) was most thoroughly studied, and a structural model is proposed. The structure of PDOPT is quite different from previously studied substituted polythiophenes in that the octyl side chains are directed normal to the thiophene planes. In this way, the conjugated polymer chains are kept separated from each other. Solution-cast and spin-cast PDOPT films are anisotropic, with the octyl side chains oriented normal to the film surface in both cases. This is contrary to the situation for poly(3-alkylthiophene)s, where solution-cast and spin-cast films orient in different ways.
|
|
| 2. |
- Chen, LC, et al.
(författare)
-
Excitation transfer in polymer photodiodes for enhanced quantum efficiency
- 2000
-
Ingår i: Advanced Materials. - 0935-9648 .- 1521-4095. ; 12:15, s. 1110-
-
Tidskriftsartikel (refereegranskat)abstract
- The realization of polymer solar cells is the driving force behind this research. In an idea inspired by photosynthesis, the authors have constructed efficient bilayer photodiodes by a well-chosen combination of conjugated polymers (see Figure) in the donor layer. Forster energy transfer within the donor layer allows the absorbed light to be channeled to the C-60 acceptor layer, improving the total photoconversion of the blend device.
|
|
| 3. |
|
|
| 4. |
|
|
| 5. |
- Inganäs, Olle, et al.
(författare)
-
Low bandgap alternating polyfluorene copolymers in plastic photodiodes and solar cells
- 2004
-
Ingår i: Applied Physics A. - : Springer Science and Business Media LLC. - 0947-8396 .- 1432-0630. ; 79:1, s. 31-35
-
Tidskriftsartikel (refereegranskat)abstract
- We report a comparative study of plastic photodiodes using four different copolymers of fluorene, with a variation of alkyl side chain length and chemical structure. Photodiode materials are formed by blending the polymers with a fullerene derivative and spincoating the blend solution. A photovoltage of 1 V is obtained in devices, where the anode is a doped polymer and the cathode is LiF/Al. Monochromatic quantum efficiencies are better than 40% over most of the absorption range, and under solar light AM 1.5 simulation, we reach energy efficiencies beyond 2%. The high fill factors obtained in some of the devices indicate that these are of interest for more elaborate optimisation. Reasons for the benign electrical transport are discussed. © Springer-Verlag 2004.
|
|
| 6. |
- Johansson, Tomas, et al.
(författare)
-
Electrochemical bandgaps of substituted polythiophenes
- 2003
-
Ingår i: Journal of Materials Chemistry. - : Royal Society of Chemistry (RSC). - 0959-9428 .- 1364-5501. ; 13:6, s. 1316-1323
-
Tidskriftsartikel (refereegranskat)abstract
- The electrochemical bandgaps for different soluble substituted polythiophenes have been measured by cyclic voltammetry. The effect of substituents on the oxidation/reduction potentials is discussed. Bandgaps obtained by cyclic voltammetry have been found to be in general higher than optical bandgaps. Among regioregular polymers substituted with a phenyl group at position 3 of the thiophene ring, examples are found that give very symmetric voltammograms. Rationalization for this behaviour is discussed from a conformational point of view.
|
|
| 7. |
- Jonforsen, M., et al.
(författare)
-
Photodiodes made from poly(pyridopyrazine vinylene) : polythiophene blends
- 2001
-
Ingår i: Synthetic metals. - 0379-6779 .- 1879-3290. ; 119:1-3, s. 185-186
-
Tidskriftsartikel (refereegranskat)abstract
- A PPV-type polymer with the pyridopyrazine heterocycle (EHH-PPyPzV) has been synthesised and found to have high electron affinity according to electrochemical measurements. When used as the electron accepting material in single-layer-photodiodes, with a thiophene copolymer (PEOPT-co-PAAPT) as the electron donating material, IPCE (incident photon to current conversion efficiency) up to 1% was measured. Atomic force microscopy was used to analyse the blend morphology in the devices.
|
|
| 8. |
- Roman, LS, et al.
(författare)
-
Trapping light in polymer photodiodes with soft embossed gratings
- 2000
-
Ingår i: Advanced Materials. - 0935-9648 .- 1521-4095. ; 12:3, s. 189-
-
Tidskriftsartikel (refereegranskat)abstract
- Increasing the conversion efficiency is very important in photovoltaic devices, as is cheap and simple technology. Here is demonstrated a soft embossing technique for printing a submicrometer grating with an elastomeric mold into an optically active polymer layer in a photovoltaic device (see Figure). The light trapping due to the grating pattern enhances the photoconversion efficiency by more than 25 % at normal light incidence (see also inside front cover).
|
|
| 9. |
- Ruseckas, A, et al.
(författare)
-
Intra- and interchain luminescence in amorphous and semicrystalline films of phenyl-substituted polythiophene
- 2001
-
Ingår i: JOURNAL OF PHYSICAL CHEMISTRY B. - : American Chemical Society (ACS). - 1089-5647 .- 1520-6106 .- 1520-5207. ; 105:32, s. 7624-7631
-
Tidskriftsartikel (refereegranskat)abstract
- We report time-resolved photoluminescence (PL) measurements of spin-cast amorphous films of a regioregular polythiophene derivative poly[3-(4-octylphenyl)thiophene] and of annealed semicrystalline films of the same polymer with an interchain stacking distance of 5 Angstrom. Red-shifted PL appears at long delay times in both pristine and annealed films, which we assign to interchain aggregates populated by excitation energy migration. Aggregate luminescence in annealed films exhibits a pronounced vibronic structure indicating the coupling to a C=C bond stretch with a Huang-Rhys factor S = 2. Two types of aggregates are distinguished in annealed films: in a few picoseconds most excitations are trapped by aggregates with a large energy gap (about 1.83 eV) between the lowest excited singlet state and the ground state. Excitation energy is transferred or the aggregates relax structurally with a time constant of about 200 ps to aggregates with a smaller energy gap (about 1.75 eV). The radiative lifetime of aggregates with smaller energy gap is estimated to be about 35 ns, two times longer than that of aggregates with the larger energy gap. In spin-cast amorphous films, emission from intrachain singlet excitons has a longer lifetime than in annealed films and only high-energy-gap aggregates are populated.
|
|
| 10. |
- Ruseckas, A., et al.
(författare)
-
Luminescence from inter-chain aggregates in polythiophene films
- 2001
-
Ingår i: Synthetic Metals. - 0379-6779 .- 1879-3290. ; 119:1-3, s. 603-604
-
Tidskriftsartikel (refereegranskat)abstract
- We report time-resolved photoluminescence of two polythiophene derivatives with different chain packing. Emission of inter-chain aggregates is distinguished from that of intra-chain singlet excitons. The aggregate luminescence is shifted towards lower energies relative to that of intra-chain exciton by 0.17 eV, and the Huang-Rhys factor of the coupling to the intra-chain C double bondC vibration is S = 1.5. The excitonic coupling in aggregates is of intermediate strength.
|
|
