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Title: Reversible Switching Between Molecular and Charge Transfer Phases in a Liquid Crystalline Organic Semiconductor

Abstract

We report the first experimental example, to our knowledge, of reversible switching between a molecular and a charge transfer phase in an organic semiconductor. An oriented film of liquid crystal perylene diimide molecules reversibly switches between a red phase with narrow conduction and valence bands and a large bandwidth black phase as the {pi}-stacked chromophores shift just 1.6 {angstrom} relative to their neighbors. This shift causes a substantial change in the intermolecular electronic overlap between molecules. The polarization of maximum absorbance rotates {approx} 90{sup o}, from an apparently molecule centered transition to an intermolecular charge transfer (CT) transition polarized along the {pi}-{pi} stacking axis. The experimental results are further explored via density functional theory calculations on a dimer model that demonstrate the variations in energy and oscillator strength of the molecular (Frenkel) and CT transitions as the longitudinal molecular offset is varied. These results demonstrate the exquisite sensitivity of the electrical properties of organic semiconductors to slight variations in molecular stacking.

Authors:
;
Publication Date:
Research Org.:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
940592
DOE Contract Number:  
AC36-99-GO10337
Resource Type:
Journal Article
Resource Relation:
Journal Name: Chemistry of Materials; Journal Volume: 20; Journal Issue: 2008
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; 36 MATERIALS SCIENCE; 37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; DIMERS; ELECTRICAL PROPERTIES; FUNCTIONALS; LIQUID CRYSTALS; ORGANIC SEMICONDUCTORS; OSCILLATOR STRENGTHS; PERYLENE; POLARIZATION; SENSITIVITY; SWITCHES; VALENCE; Chemical and Biosciences

Citation Formats

Gregg, B. A., and Kose, M. E. Reversible Switching Between Molecular and Charge Transfer Phases in a Liquid Crystalline Organic Semiconductor. United States: N. p., 2008. Web. doi:10.1021/cm800813h.
Gregg, B. A., & Kose, M. E. Reversible Switching Between Molecular and Charge Transfer Phases in a Liquid Crystalline Organic Semiconductor. United States. doi:10.1021/cm800813h.
Gregg, B. A., and Kose, M. E. Tue . "Reversible Switching Between Molecular and Charge Transfer Phases in a Liquid Crystalline Organic Semiconductor". United States. doi:10.1021/cm800813h.
@article{osti_940592,
title = {Reversible Switching Between Molecular and Charge Transfer Phases in a Liquid Crystalline Organic Semiconductor},
author = {Gregg, B. A. and Kose, M. E.},
abstractNote = {We report the first experimental example, to our knowledge, of reversible switching between a molecular and a charge transfer phase in an organic semiconductor. An oriented film of liquid crystal perylene diimide molecules reversibly switches between a red phase with narrow conduction and valence bands and a large bandwidth black phase as the {pi}-stacked chromophores shift just 1.6 {angstrom} relative to their neighbors. This shift causes a substantial change in the intermolecular electronic overlap between molecules. The polarization of maximum absorbance rotates {approx} 90{sup o}, from an apparently molecule centered transition to an intermolecular charge transfer (CT) transition polarized along the {pi}-{pi} stacking axis. The experimental results are further explored via density functional theory calculations on a dimer model that demonstrate the variations in energy and oscillator strength of the molecular (Frenkel) and CT transitions as the longitudinal molecular offset is varied. These results demonstrate the exquisite sensitivity of the electrical properties of organic semiconductors to slight variations in molecular stacking.},
doi = {10.1021/cm800813h},
journal = {Chemistry of Materials},
number = 2008,
volume = 20,
place = {United States},
year = {Tue Jan 01 00:00:00 EST 2008},
month = {Tue Jan 01 00:00:00 EST 2008}
}