Probing of. pi. conjugation in trans -polyacetylene using near-infrared photoluminescence spectroscopy
Abstract
Near-infrared photoluminescence from undoped {ital trans}-polyacetylene was attributed to emission from {ital cis} defects,'' structures composed of isolated bonds embedded within conjugated {ital trans}-(CH){sub {ital x}} segments. Spectra were found to be independent of residual transition-metal impurities in the polymer, but quantum efficiencies decreased with increasing concentrations of neutral defects and free carriers. The percolation limit for free carriers was achieved at about 30% overall {ital trans}-(CH){sub {ital x}}. The photoluminescence energy varied inversely with the length of the conjugated {ital cis} defects, with a different dependence than for polyenes in solution. Interchain interactions were found to be significant in the solid state, distorting bonding geometries and perturbing the electronic structure of the chains; we postulate they are essential for bulk conduction. Hueckel calculations yielded {beta}{sub 0}=1.08 eV for the {pi} interaction energy, predicting an energy of 0.39--0.43 eV for the {pi}-{pi}{sup *} transition of a typical bound neutral soliton. The band gap for {ital trans}-polyacetylene of infinite conjugation length was estimated to be 1.20 eV by extrapolation of the solid-state luminescence data. We conclude that thermally isomerized {ital trans}-polyacetylene is best described as being a three-dimensional ensemble of short, conjugated segments that are bounded and interconnected by defects andmore »
- Authors:
-
- Department of Chemistry, University of California, Berkeley, Berkeley, California 94720 (USA)
- Department of Chemistry, University of California, Berkeley, Berkeley, California 94720 (USA) Lawrence Berkeley Laboratory, Berkeley, California 94720 (USA)
- Publication Date:
- OSTI Identifier:
- 5555924
- Resource Type:
- Journal Article
- Journal Name:
- Physical Review, B: Condensed Matter; (USA)
- Additional Journal Information:
- Journal Volume: 43:18; Journal ID: ISSN 0163-1829
- Country of Publication:
- United States
- Language:
- English
- Subject:
- 37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; 36 MATERIALS SCIENCE; POLYACETYLENES; ELECTRONIC STRUCTURE; CARRIER DENSITY; CHAINS; CHEMICAL BONDS; DEFECTS; EXCITONS; HYBRIDIZATION; NEAR INFRARED RADIATION; PHOTOLUMINESCENCE; QUANTUM EFFICIENCY; RECOMBINATION; SPECTROSCOPY; EFFICIENCY; ELECTROMAGNETIC RADIATION; HYDROCARBONS; INFRARED RADIATION; LUMINESCENCE; ORGANIC COMPOUNDS; POLYENES; QUASI PARTICLES; RADIATIONS; 400500* - Photochemistry; 360603 - Materials- Properties
Citation Formats
Carter, P W, and Porter, J D. Probing of. pi. conjugation in trans -polyacetylene using near-infrared photoluminescence spectroscopy. United States: N. p., 1991.
Web. doi:10.1103/PhysRevB.43.14478.
Carter, P W, & Porter, J D. Probing of. pi. conjugation in trans -polyacetylene using near-infrared photoluminescence spectroscopy. United States. https://doi.org/10.1103/PhysRevB.43.14478
Carter, P W, and Porter, J D. 1991.
"Probing of. pi. conjugation in trans -polyacetylene using near-infrared photoluminescence spectroscopy". United States. https://doi.org/10.1103/PhysRevB.43.14478.
@article{osti_5555924,
title = {Probing of. pi. conjugation in trans -polyacetylene using near-infrared photoluminescence spectroscopy},
author = {Carter, P W and Porter, J D},
abstractNote = {Near-infrared photoluminescence from undoped {ital trans}-polyacetylene was attributed to emission from {ital cis} defects,'' structures composed of isolated bonds embedded within conjugated {ital trans}-(CH){sub {ital x}} segments. Spectra were found to be independent of residual transition-metal impurities in the polymer, but quantum efficiencies decreased with increasing concentrations of neutral defects and free carriers. The percolation limit for free carriers was achieved at about 30% overall {ital trans}-(CH){sub {ital x}}. The photoluminescence energy varied inversely with the length of the conjugated {ital cis} defects, with a different dependence than for polyenes in solution. Interchain interactions were found to be significant in the solid state, distorting bonding geometries and perturbing the electronic structure of the chains; we postulate they are essential for bulk conduction. Hueckel calculations yielded {beta}{sub 0}=1.08 eV for the {pi} interaction energy, predicting an energy of 0.39--0.43 eV for the {pi}-{pi}{sup *} transition of a typical bound neutral soliton. The band gap for {ital trans}-polyacetylene of infinite conjugation length was estimated to be 1.20 eV by extrapolation of the solid-state luminescence data. We conclude that thermally isomerized {ital trans}-polyacetylene is best described as being a three-dimensional ensemble of short, conjugated segments that are bounded and interconnected by defects and crosslinks. Mean segment lengths are probably less than 13 units.},
doi = {10.1103/PhysRevB.43.14478},
url = {https://www.osti.gov/biblio/5555924},
journal = {Physical Review, B: Condensed Matter; (USA)},
issn = {0163-1829},
number = ,
volume = 43:18,
place = {United States},
year = {Sat Jun 15 00:00:00 EDT 1991},
month = {Sat Jun 15 00:00:00 EDT 1991}
}