| 21. |
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| 22. |
- Theander, M., et al.
(författare)
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High luminescence from a substituted polythiophene in a solvent with low solubility
- 2001
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Ingår i: Chemical Physics Letters. - 0009-2614 .- 1873-4448. ; 337:4-6, s. 277-283
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Tidskriftsartikel (refereegranskat)abstract
- Steady-state and rime-resolved photoluminescence (PL) is used to probe different states of order in highly regular poly(3-(2'-methoxy-5'-octylphenyl)thiophene) (POMeOPT). In a good solvent (chloroform) the polymer has a PL yield of 0.33 and in a solvent with low solubility (mixture of chloroform and toluene) a new phase appears with higher PL yield (0.50). The new phase is attributed to micro-crystals formed by the regular part of the polymer which have low solubility in toluene. The crystallites have highly structured and redshifted electronic transitions compared with chains which are dissolved. (C) 2001 Published by Elsevier Science B.V.
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| 23. |
- Theander, M., et al.
(författare)
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Interchain photoluminescence in substituted polyfluorenes
- 2001
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Ingår i: Synthetic metals. - 0379-6779 .- 1879-3290. ; 119:1-3, s. 615-616
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Tidskriftsartikel (refereegranskat)abstract
- We have characterised the interchain emitting states of two substituted polyfluorenes with steady-state and time-resolved photoluminescence (PL). Site selective excitation of the interchain state shows that physical dimers are formed in the film. These dimers have low concentration in the films but exciton diffusion to the dimers is reducing the intrachain exciton lifetime. With asymmetrical substituents, the PL quantum yield is higher and the PL lifetime is longer due to lower concentration of dimers. Slow cooling from the melt, gives a new red shifted emission band and less intrachain emission. A discrepancy in the calculated radiative lifetimes suggest a fast formation of this new band.
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| 24. |
- Theander, M., et al.
(författare)
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Photoluminescence quenching at a polythiophene/C-60 heterojunction
- 2000
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Ingår i: Physical Review B (Condensed Matter and Materials Physics). - 1098-0121 .- 1550-235X. ; 61:19, s. 12957-12963
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Tidskriftsartikel (refereegranskat)abstract
- Quenching of photoluminescence in a substituted polythiophene in the presence of a deposited C-60 layer is studied by steady-state and time-resolved photoluminescence (PL). The steady-state PL is evaluated by con -sidering the interference of the absorbed and emitted electro-optical field in the thin film coupled to exciton diffusion in the conjugated polymer. PL quenching occurs for excitons generated within 5 nm from the heterojunction. A blueshift of the polymer emission spectrum is observed when C-60 is deposited on top of a polymer thin film. The blueshift is shown to be caused by PL quenching before the excitation is transferred to the lowest-energy sites.
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| 25. |
- Wang, Xiangjun, et al.
(författare)
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Electrophosphorescence from polythiophene blends light-emitting diodes
- 2003
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Konferensbidrag (refereegranskat)abstract
- Electrophosphorescence has been observed in phosphorescent blend polythiophene LEDs with poly(3-methyl-4-octyl-thiophene) (PMOT) as host, bis (2-phenylbenzothiazole) iridium acetylacetonate (BTIr) as the guest. Investigation of photoluminescence and quantum yields shows that energy transfer exists in the host-guest system and depends on guest concentration. Electroluminescence indicates that charge trapping effect also contributes to the formation of exciton at phosphorescent centers.
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| 26. |
- Yohannes, T., et al.
(författare)
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Polyfluorene copolymer based bulk heterojunction solar cells
- 2004
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Ingår i: Thin Solid Films. - 0040-6090 .- 1879-2731. ; 449:1-2, s. 152-157
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Tidskriftsartikel (refereegranskat)abstract
- Bulk heterojunction solar cells based on blends of photoactive layers of polyfluorene copolymer Poly((2,7-(9-(2'-ethylhexyl)-9-hexyl-fluorene)-alt-5,5-(4', 7'-di-2-thienyl-2',1',3'-benzothiadiazole))-co-(2, 7-(9-(2'-ethylhexyl)-9-hexyl-fluorene)-alt-2,5-thiophene)) (LBPF3) acting as electron donor, and [6,6]-phenyl-C61-butyric acid methylester (PCBM), acting as electron acceptor, were constructed and studied. The power conversion efficiency for a 1:4 (by weight) blend of LBPF3:PCBM under simulated solar light illumination having light intensity of 100 mW/cm2 was 1.7%, and 9.2% under monochromatic (565 nm) light illumination with light intensity of 0.145 mW/cm2. The maximum external quantum efficiency (incident photons to converted electrons) for this device was found to be above 40% from 400 to 560 nm. The effects of blend composition and film thickness on the photovoltaic parameters were also studied. The incident light intensity dependence of the short circuit current showed a linear relationship. © 2003 Elsevier B.V. All rights reserved.
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| 27. |
- Zhang, Fengling, et al.
(författare)
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Influence of buffer layers on the performance of polymer solar cells
- 2004
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 84:19, s. 3906-3908
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Tidskriftsartikel (refereegranskat)abstract
- The study of the influence of different anode buffer layers on the performance of solar cells based on blends of polyfluorene copolymers, acting as electron donor, and [6,6]-phenyl-C61-butyric acid methylester (PCBM), acting as electron acceptor was presented. The construction of buffer later was done from different forms of poly(3, 4-ethylenedioxythiophene) poly-(styrenesulfonate) (PEDOT-PSS). Variations in open-circuit voltage, short-circuit current and fill factor were also observed. The anode buffer layer influences the photovoltage of polymer solar cells by controlling the conditions for charge injection at the anode.
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| 28. |
- Zhang, Fengling, et al.
(författare)
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Photodiodes and solar cells based on the n-type polymer poly(pyridopyrazine vinylene) as electron acceptor
- 2003
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Ingår i: Synthetic metals. - 0379-6779 .- 1879-3290. ; 138:3, s. 555-560
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Tidskriftsartikel (refereegranskat)abstract
- The photodiodes and solar cells based on the n-type polymer poly(pyridopyrazine vinylene) as electron acceptor were discussed. It was found that the external quantum efficiency of these diodes reached 7%. The analysis showed that under low-intensity monochromatic light, the open circuit voltage reached 900 mv.
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| 29. |
- Zhang, Fengling, et al.
(författare)
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Polymer solar cells based on MEH-PPV and PCBM
- 2003
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Konferensbidrag (refereegranskat)abstract
- Polymer solar cells based on poly(2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylene vinylene(MEH-PPV) and fullerene derivative [6,6]phenyl-C61butyric acid methyl ester (PCBM) were fabricated by spin-coating. The improved performance has been achieved by blend polymer MEH-PPV with PCBM in a ratio of 1:4 by weight. The power conversion efficiency reached 1.3% under illumination of AM 1.5 with an incident power density of 78 mW/cm2 in blend single layer polymer solar cells.
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