| Item type: | Article | ||||
|---|---|---|---|---|---|
| Journal or Publication Title: | Synthetic Metals | ||||
| Publisher: | ELSEVIER SCIENCE SA | ||||
| Place of Publication: | LAUSANNE | ||||
| Volume: | 140 | ||||
| Number of Issue or Book Chapter: | 2-3 | ||||
| Page Range: | pp. 155-170 | ||||
| Date: | 2004 | ||||
| Institutions: | Physics > Institute of Experimental and Applied Physics > Alumni or Retired Professors > Group Alfons Penzkofer | ||||
| Identification Number: |
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| Keywords: | SOLID-STATE LASERS; EXCITON-EXCITON ANNIHILATION; LIGHT-EMITTING-DIODES; AMPLIFIED SPONTANEOUS EMISSION; OPTICAL-CONSTANTS MEASUREMENT; EFFECTIVE STIMULATED-EMISSION; CROSS-SECTION SPECTRA; CONJUGATED POLYMERS; THIN-FILMS; SEMICONDUCTING POLYMERS; MEH-PPV luminescent polymers; amplified spontaneous emission; travelling-wave laser action; optical constants; absorption spectra; fluorescence spectroscopy | ||||
| Dewey Decimal Classification: | 500 Science > 530 Physics | ||||
| Status: | Published | ||||
| Refereed: | Yes, this version has been refereed | ||||
| Created at the University of Regensburg: | Yes | ||||
| Item ID: | 71742 |
Abstract
Two different types of poly(2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylene-vinylene) (MEH-PPV) (i) a strictly linear, well-defined material of moderate molar mass prepared through polycondensation (Homer-type) and (ii) a commercially available MEH-PPV-sample (Gilch-type, high-molecular and defect-rich) resulting from a dehydrohalogenation process, are carefully analysed by GPC and C-13/H-1-NMR ...
Abstract
Two different types of poly(2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylene-vinylene) (MEH-PPV) (i) a strictly linear, well-defined material of moderate molar mass prepared through polycondensation (Homer-type) and (ii) a commercially available MEH-PPV-sample (Gilch-type, high-molecular and defect-rich) resulting from a dehydrohalogenation process, are carefully analysed by GPC and C-13/H-1-NMR spectroscopy. These studies show that for the Gilch-type polymer there is a marked deficiency of regular vinylene groups (approximate to30%), and therefore, a lack of long-range polyconjugation. The samples are characterized by thin-film optical constants measurements, absorption and fluorescence spectroscopic studies, and thin-film wave-guided travelling-wave laser action investigations. The influence of film-forming solvents (chlorobenzene (CB), tetrahydrofuran (THF)) and of film heating on the absorption, emission and laser behaviour is investigated. The fluorescence quantum yields of neat films (approximate to25% for Homer-type MEH-PPV and approximate to36% for Gilch-type MEH-PPV) and toluene solutions (approximate to38% for Homer-type MEH-PPV and approximate to32% for Gilch-type MEH-PPV) are similar. The exciton delocalisation (chromophore size) is found to be about four repeat units for both types of MEH-PPV. Remarkably good laser performance with low pump laser threshold (<20 muJ/cm(2)) was achieved for both polymers independent of the synthesis pathway, the deviations in the molecular fine structure and the film-forming solvents. However, the preparation of high quality optical films is much easier for the Homer-type MEH-PPV than for the Gilch-type MEH-PPV making the Homer-type MEH-PPV easier to use for thin-film lasers and photonic devices. (C) 2003 Elsevier B.V. All rights reserved.
Metadata last modified: 19 Dec 2024 15:16
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