Photovoltaic heterostructure devices made of sequentially adsorbed poly(phenylene vinylene) and functionalized C60

We report on the preparation and characterization of rectifying photovoltaic heterostructure devices made of poly(phenylene vinylene), PPV, and C60. The heterojunctions were built from solution using the technique of layer-by-layer sequential adsorption. This technique permits one to control the heterostructure 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 the C60 (acceptor layer). The photocurrent was found to increase with the laser power and with the photon energy of the incident radiation. Also, a constant high photovoltage response of ∼700–800 mV was measured. Analysis of the time dependence of the photocurrent rise and decay, when the device was illuminated with a modulated square wave signal (chopped laser beam), permitted us to draw an analogy between the present heterojunction and a circuit made of a capacitor and a resistance in series.