Light-induced switching in the back-gated organic transistors with   built-in conduction channel
  We report on observation of a light-induced switching of the conductance in the back-gated organic field-effect transistors (OFETs) with built-in conduction channel. In the studied devices, the built-in channel is formed owing to the self-sensitized photo-oxidation of rubrene surface. In the dark, the back gate controls the charge injection from metal contacts into the built-in channel: the high-current ON state corresponds to zero or negative back-gate voltage; the low-current OFF state - to a positive back-gate voltage that blocks the Schottky contacts. Illumination of the OFET in the OFF state with a short pulse of light switches the device into the ON state that persists in the dark for days. The OFF state can be restored by cycling the back gate voltage. The observed effect can be explained by screening of the back-gate electric field by the charges photo-generated in the bulk of organic semiconductor. 
V. Podzorov, V. M. Pudalov, M. E. Gershenson