Stray-light induced artefacts in absorption spectra of crystalline oligothiophenes

The absorption spectra of oligothiophene single crystals and thin films are discussed in terms of stray light induced experimental artefacts. After typical experimental problems have been overcome, absorption spectra can be collected over a wide spectral range in the UV-Vis region that has often not been included in the literature data. A clear similarity is found between the absorption spectra of single crystals and highly ordered thin films