Reversible Switching between Molecular and Charge Transfer Phases in a Liquid Crystalline Organic Semiconductor
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 ba...
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Published in | Chemistry of materials Vol. 20; no. 16; pp. 5235 - 5239 |
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Main Authors | , |
Format | Journal Article |
Language | English |
Published |
American Chemical Society
26.08.2008
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Subjects | |
Online Access | Get full text |
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Summary: | 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 π-stacked chromophores shift just 1.6 Å relative to their neighbors. This shift causes a substantial change in the intermolecular electronic overlap between molecules. The polarization of maximum absorbance rotates ∼90°, from an apparently molecule centered transition to an intermolecular charge transfer (CT) transition polarized along the π−π 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. |
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Bibliography: | istex:1B3270C1BC3668F248C95026E7F917039A6EEFF3 ark:/67375/TPS-0QNGH93M-M |
ISSN: | 0897-4756 1520-5002 |
DOI: | 10.1021/cm800813h |