Alan J. Heeger and colleagues point out that plastic solar cells, fabricated from bulk heterojunction materials comprising semiconducting polymers and fullerenes, have already demonstrated promising performance. However, researchers do not understand how to control the nano-scale morphology and are looking for ways to optimize the solar cell performance for practical use. Heeger, co-recipient of the Nobel Prize in Chemistry in 2000 for his pioneering research on conducting polymers, is widely recognized for his ongoing efforts to improve solar cell efficiencies.