Organic donor/acceptor photovoltaics:: The role of C60/metal interfaces

The photovoltaic properties of thin films based on donor/acceptor heterojunctions, prepared by means of either consecutive evaporation or co-evaporation, and sandwiched between asymmetric contacts are investigated. (E,E,E,E)-1,4-bis[(4-styryl)styryl]-2-methoxy-5-(2'-ethylhexoxy)benzene (MEH-OPV5) and Buckminster fullerene C-60 are employed as donor and acceptor materials, respectively. Current-voltage measurements and impedance spectroscopy on the donor and the acceptor single-layer cells suggest the presence of a strong dipole layer at the C-60/metal interfaces. The correlation between the photovoltaic performances and film morphologies is discussed. (C) 2003 American Institute of Physics.