  We present a methodology for computing photocurrent production in molecular
semiconducting molecules. Our model combines a single-configuration interaction
picture with the Schwinger-Keldysh non-equilibrium Greens function approach to
compute the current response of a molecular semi-conducting wire following
excitation. We give detailed analysis of the essential excitonic,
charge-transfer, and dipole states for poly-(phenylenevinylene) chains of
length 32 and 48 repeat units under an electric field bias and use this to
develop a reduced dimensional tunneling model which accounts for chain-length
and field-dependent behavior.
