Separating electrons and holes:  A prerequisite for photovoltaic applications
Blending C60 and p-conjugated polymer
Nearly 100% electron transfer to the C60
Because of bipolaron BP2+ formation minimal back transfer
Polymer has good hole mobilities
Design of interface and electron transport are bottle necks
Recombination of P+ and P- reduces device efficiency
From: Christoph J. Brabec, N. Serdar Sariciftci, and Jan C. Hummelen, Advanced Functional Materials 11 (2001).