4.2% efficient organic photovoltaic cells with low series resistances

We demonstrate double-heterostructure copper phthalocyanine/C-60 organic photovoltaic cells with series resistances as low as 0.1 Omega cm(2). A high fill factor of similar to0.6 is achieved, which is only slightly reduced at very intense illumination. As a result, the power conversion efficiency increases with the incident optical power density, reaching a maximum of (4.2+/-0.2)% under 4-12 suns simulated AM1.5G illumination. The cell performance is accurately described employing an analysis based on conventional semiconductor p-n junction diodes. The dependence of the series resistance on the device area suggests the dominance of the bulk resistance of the indium-tin-oxide anode as a limiting factor in practical cell efficiencies. (C) 2004 American Institute of Physics.