Photoluminescence properties of polythiophenes

We have characterised two polythiophenes, poly(3-(2,5-octyldiphenyl)-thioph ene) (PDOPT) and poly(3-(4-octylphenyl)-2,2'-bithiophene) (PTOPT), with res pect to their Pt properties both in film and solution. PDOPT is highly regu lar and has large sidegroups which make the backbone rigid; the Pt yield is 0.37 in solution. For thin films, the high regularity makes the polymer pa rtially crystalline. The bulky sidechains efficiently separates the backbon es giving the polymer a high Pt yield (0.24). PTOPT have a low density of s idechains, and the PL yield reduces from 0.27 to 0.05 going from solution t o thin film. Poly(3-methyl-4-octyl-thiophene) (PMOT) is twisted out of plan arity by sterical hindrance and shows blueshifted absorption and emission. We show that PMOT have low PL yield in solution due to nonradiative decay w ith short lifetime.