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Title: 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 » crosslinks. Mean segment lengths are probably less than 13 units.« less

Authors:
 [1];  [2]
  1. Department of Chemistry, University of California, Berkeley, Berkeley, California 94720 (USA)
  2. 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}
}