Thin Solid Films, Vol.403-404, 419-424, 2002
Optical and electrooptical absorption in conducting polymers
We describe effects of the long-range Coulomb interactions on absorption and photoconductivity of polymeric semi conductors. The final-state interaction suppresses the ID edge singularity of band-to-band transitions, reducing it to the final value. This value meets the averaged subgap absorption through the high excitonic series below the gap. After a dip. the absorption increases at the primary exciton peak. At moderately strong electric fields, higher excited states are destroyed, while the primary one is preserved. Our results explain the rounding of the e-h absorption edge observed in various polymeric semiconductors. Moreover, they quantitatively agree with new photoconductivity data on PPV-type polymers where new spectral features appear under electric field.