Screening by space charge layers and self-localization in conjugated polymers

In devices, strong electric fields do occur at interfaces between the active semiconductor and oxides, metals or other semiconductors. They are screened by space charge layers (SCL) in the semiconductor. We describe the influence of (bi)polaronic states and bipolaron lattice formation on SCL, and we discuss in detail the consequences of such states. A singularity of the capacity (maximum at finite T) is caused primarily by one-dimensionality (not by self-localization), and does not lead to a Fermi level pinning as stated before.