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Intrinsic excitonic luminescence in odd and even numbered oligothiophenes
F Meinardi1, M Cerminara, A Sassella
1INFM and Department of Material Science, University of Milano-Bicocca, via Cozzi 53, Italy.
Physical Review Letters
|October 9, 2002
Abstract:
The emission properties of crystalline oligothiophenes (OTs) are investigated and related to the different selection rules arising from the number of rings. In odd OT crystals the purely electronic emission is absent since the molecular A1-1B(1) transition dipoles cancel at the bottom of the excitonic band. On the contrary, in crystals of even OTs this transition is allowed due to the constructive interference of the off-axis components of the molecular transition dipole. It possesses a polarization in the herringbone plane and exhibits superradiant behavior.