Effect of Hydrostatic Pressure on the Absorption Spectrum of Poly(3-alkylthiophene) Solution

Abstract
The absorption edge of poly(3-hexylthiophene) in toluene demonstrates a remarkable red shift upon application of high hydrostatic pressure. A band gap as small as 1.7 eV has been evaluated in this solution under hydrostatic pressure. This is much smaller even than that of a nonsubstituted polythiophene film (2.0 eV) and is explained by the increased co-planarity due to the decreased torsion angle between neighboring thiophene rings.