Optical properties of light-emitting nematic liquid crystals: a joint experimental and theoretical study.
Semiempirical quantum-chemical calculations are used to simulate the optical properties of a series of green light-emitting nematic liquid crystals containing fluorene, thiophene, or thienothiophene groups with solid-state photoluminescence quantum efficiencies up to 0.36. We use a simple model of two parallel and closely spaced molecules in an anticofacial configuration to study intermolecular interactions in the solid state and slide one past the other to mimic the high orientational and low positional order of the nematic phase. We find that switching between H and J aggregates can be triggered by longitudinal displacements of the molecules with respect to one another by an extent that closely follows the chemical structure of the interacting chromophores. We discuss the implications of aggregate formation for efficient light emission in conjugated oligomers and polymers that show nematic or smectic order.
Liedtke
Alicia
A
Department of Physics, University of Hull, Cottingham Road, Hull, HU6 7RX, UK.
O'Neill
Mary
M
Kelly
Stephen M
SM
Kitney
Stuart P
SP
Van Averbeke
Bernard
B
Boudard
Pol
P
Beljonne
David
D
Cornil
Jérôme
J