Spatial conformation and charge recombination properties of polythiophene derivatives with thienylene-vinylene side chains investigated by static and femtosecond spectroscopy.
We report herein the photophysics of three two-dimensional polythiophene derivatives, with different lengths of thienylene-vinylene conjugated side chains, in comparison with regioregular poly(3-hexylthiophene) (P3HT). In solution, an evolution from stimulated emission to photoinduced absorption (PIA) at emission peak is discovered with increasing length of side chains, indicating larger steric hindrance by longer side chains. The exciton lifetime is reduced by a factor of five when the thienylene-vinylene side chain is prolonged to three units. In the film form, we investigate the dynamics of the two PIA bands, assigned to intrachain exciton and interchain polaron pairs, respectively. The analysis of the dynamics suggests that their intrachain exciton decays are similar to the one-dimensional P3HT. The recombination possibility of delocalized interchain polaron pairs occurring in 0.9 ps is reduced with longer thienylene-vinylene side chain samples. Compared with regioregular P3HT film, which self-organizes to form lamellae crystal morphology, the morphologies of these three two-dimensional polythiophenes are amorphous, attributed to the large steric hindrance caused by the existence of side chains. This design of polythiophene derivatives provides the reduction of recombination possibility for delocalized interchain polaron pairs generated in the polymer.
Meng
Kang
K
State Key Laboratory for Mesoscopic Physics, Department of Physics, Peking University, Beijing, China, 100871.
Ding
Qing
Q
Wang
Shufeng
S
He
Youjun
Y
Li
Yongfang
Y
Gong
Qihuang
Q
D008567:Membranes, Artificial; D008968:Molecular Conformation; D013050:Spectrometry, Fluorescence; D013056:Spectrophotometry, Ultraviolet; D013876:Thiophenes / Q000737:chemistry*; D014753:Vinyl Compounds / Q000737:chemistry*; D014961:X-Ray Diffraction
D008567:Membranes, Artificial; D013876:Thiophenes; D014753:Vinyl Compounds