Researchers at the Massachusetts Institute of Technology (MIT; Cambridge, MA), the University of Massachusetts (Lowell, MA), and National Taiwan University (Taipei, Taiwan) have used poly(phenylene vinylene) (PPV) and buckminsterfullerene (C60) to fabricate a circuit of rectifying photovoltaic heterostructure devices analogous to a capacitor and resistor in series. Layer-by-layer sequential adsorption was used to build the heterojunctions from solution. Current and voltage photoresponses were observed upon laser illumination that increased with incident laser power and photon energy to a high-end photovoltage response on the order of 800 mV.

The actual alternating electron donor and acceptor layers consisted of PPV/poly(acrylic acid) and C60/poly(allyl amine hydrochloride), respectively. They were built on glass slides patterned with 200-nm-thick stripes of indium tin oxide (ITO). Four aluminum electrodes evaporated orthogonal to the ITO provided individually addressable cells. Photostimulation was applied at 457, 488, and 514 nm. Potential short-term applications include fabrication of sensitive solar cells with low dark currents and high open-circuit voltages, according to the researchers. Potential long-term applications include facilitating study of charge-transfer processes between conjugated polymers and C60. Contact Hedi Mattoussi at hedimat@ccs.nrl.navy.mil.