The optical properties of ordered and disordered α-sexithiophene (α-6T) thin films are investigated by a variety of spectroscopies. The dominant low-lying even and odd parity excitons are identified by absorption and electroabsorption spectroscopies. Intermolecular interactions in ordered α-6T films results in Davydov splitting of the absorption band of the lowest odd parity exciton. charged excitations in α-6T films were studied by photoinduced absorption and optically detected magnetic resonance. Both polarons and bipolarons are observed in disordered samples. As a consequence of higher carrier mobilities, only bipolarons were observed in ordered samples. Spin pairing of excitations broadens the observed ODMR spectra.
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