Recently, upon mixing buckminsterfullerene, C-60, into semiconducting conjugated polymers, an interesting photophysical phenomenon has been discovered. The photoinduced electron transfer from semiconducting polymers onto C-60 is reversible, ultrafast with a quantum efficiency approaching unity, and metastable. This photoinduced electron transfer leads to a number of potentially interesting applications, including photodetectors and photovoltaic cells. In this work, we briefly present the photo-physics and associated device applications of conjugated polymer-fullerene composites. (C) 2003 Elsevier B.V. All rights reserved.