Organic solar cells: an overview focusing on active layer morphology.

Solar cells constructed of organic materials are becoming increasingly efficient due to the discovery of the bulk heterojunction concept. This review provides an overview of organic solar cells. Topics covered include: a brief history of organic solar cell development; device construction, definitions, and characteristics; and heterojunction morphology and its relation to device efficiency in conjugated polymer/fullerene systems. The aim of this article is to show that researchers are developing a better understanding of how material structure relates to function and that they are applying this knowledge to build more efficient light-harvesting devices.