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on a 220-nm-thick film. The conversion efficiency is equal to 0.01% under 100 mW cm 22 white light illumination. Effects of dye loading, film thickness, and light intensity are described. A model based on simple assumptions is used to fit the photoaction spectra. By evaporation under vacuum of a layer of N,N8-dimethyl-3,4,9,10-perylenetetracarboxylic diimide between the ITO and the polymer film, we have fabricated hybrid polymer-molecularp ‐n type photovoltaic cells. The role of this molecule in the photogeneration has been studied. A constant power conversion efficiency of 0.15% has been measured under white light illumination between 0.2 and 200 mW cm 22 .© 2001

Light-emitting diodes made of a single spin-coated layer of poly(9-vinylcarbazole) have been doped with coumarin-515 dye and the effect of the dye concentration on emission and electrical characteristics has been studied. Two different regimes have been identified. For low concentrations, the apparent hole injection barrier rises, holes are trapped, and mobility decreases. External quantum efficiency increases with concentration. At concentrations larger than 10 wt % coumarin aggregates, photoluminescence yield drops and electroluminescence yield increases up to 0.1% photons per electron. As a conclusion, using coumarin dye in a single-layer diode improves electron–hole injection and recombination balance more than using an additional hole-blocking layer.