Charge carrier generation and electron blocking at interlayers in polymer solar cells

The authors show that an electron-donating polymer interlayer and a spin coated layer of an electron-accepting polymer form a defined polymer-polymer heterojunction. Directional photoinduced charge transfer and efficient electron blocking at this heterojunction is clearly seen in Kelvin probe measurements. The photocurrent characteristics of this well-defined bilayer structure as well as of the respective blend device can be consistently fitted by models taking into account only the field dependence of charge carrier generation. Apparently, the efficiency to form free carriers is the determining process in both types of polymer-polymer solar cell structures. (c) 2007 American Institute of Physics.