Photovoltaic heterostructure devices made of sequentially adsorbed poly(phenylene vinylene) and functionalized C-60

We report on the preparation and characterization of rectifying photovoltai c heterostructure devices made of poly(phenylene vinylene), PPV, and C-60. The heterojunctions were built from solution using the technique of layer-b y-layer sequential adsorption. This technique permits one to control the he terostructure at the molecular scale. Upon illumination with a laser beam, the devices showed large photoresponses (current and voltage) that resulted from a photoinduced electron transfer between the PPV (donor layer) and th e C-60 (acceptor layer). The photocurrent was found to increase with the la ser power and with the photon energy of the incident radiation. Also, a con stant high photovoltage response of similar to 700-800 mV was measured. Ana lysis of the time dependence of the photocurrent rise and decay, when the d evice was illuminated with a modulated square wave signal (chopped laser be am), permitted us to draw an analogy between the present heterojunction and a circuit made of a capacitor and a resistance in series. (C) 2000 America n Institute of Physics. [S0003-6951(00)03236-8].