Conjugated oligothiophenes, electronic excited

Although the electronic properties of oligothiophenes have already been reviewed [29, 30], the picture of the nature and ordering of the electronic states in the solid state is still diffuse and incoherent. Therefore we will cover recent results on the optical properties especially in the soUd state and the outcome may lead to a clearer picture of the excited state ordering. This may even contribute to a better understanding of the electronic states for other rigid-rod-like conjugated materials. 

The results of photoinduced absorption in polymer solutions and oligothiophene films and solutions (see Sections 3 and 4) show a profound effect of the surrounding medium on the character of the photo-excited species. Based on these results, we inferred that for pristine conjugated polymers embedded in a nonpolar medium, neutral photoexcitations are favored, whereas in polar media, charged and neutral photoexcitations co-exist. In conjugated polymer/C6o mixtures, embedded in a non-polar medium, energy transfer and triplet sensitization are favored, whereas in polar media, photoinduced electron transfer phenomena clearly dominate. 

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