Intrinsic Photoconduction in PPV-Type Conjugated Polymers

Steady state photoconduction experiments have been performed on thin films of derivatives of polyphenylenevinylene contacted in sandwich configuration. The use of a silicon monoxide blocking layer allows the separation of intrinsic from extrinsic photocurrents. Intrinsic photogeneration increases with electric field, temperature, and photon energy in agreement with the 3D version of Onsager's theory of geminate pair dissociation adapted to energetically random hopping systems. The thermalization distance, which determines the escape rate, increases with the effective conjugation length of the chain segments. The average energy required to dissociate a confined on-chain excitation is 0.4 eV.