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					                     Role of Nematic Order in Conjugated Polymer Spectroscopy

                                              Michael Winokur
                                University of Wisconsin, Madison, WI, USA

                                                ABSTRACT

Conjugated polymers (CPs) now form the basis for a broad spectrum of new devices technologies (e.g.,
plastic transistors, organic photovoltaics, polymer light emitting diodes). These fascinating materials
combine many attributes traditionally found in inorganic semiconductors with those of soft condensed
matter. CPs in the solid-state undergo a hierarchical structural ordering spanning vastly different length
scales. These include the inherent structure of the conjugated polymer film, its structure at an interface and,
finally, the interaction between the interfacial and interior ordering. Nematic alignment, a characteristic
widely seen in these optically active polymers, creates an environment in which overlap between the
chromophore absorption and emission bands can lead to large scale self-absorption of the * emission
band even in moderately thin films.[1] This nematic order also affects simple absorption measurements.
Steady-state optical emission and absorption measurements of the blue emitting polymer poly[bis(2-
ethyl)hexylfluorene] in combination with modeling by a transfer matrix approach are used to demonstrate
the impact of these effects.

References

[1] M.J. WINOKUR, H. CHEUN, M. KNAAPILA, A.P. MONKMAN, U. SCHERF, Phys. Rev. B. 75
(2007) 11320.

				
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