- Conjugated polymers and carbon nanotubes (CNTs) are important constituents of modern functional hybrid materials. Their utilization as photoactive layers in organic solar cells requires better understanding of the relation between the structure and composition of the hybrids and their photovoltaic efficiency. While fullerenes-conjugated polymer hybrids have been intensively studied over the last two decades, far less is known about the linkage between processing conditions, interfacial interactions, self-assembled structures and functionality in CNT-conjugated polymers composites. This article reviews some of the studies carried over the last decade and highlights the challenges in both fundamental understanding and technological manipulation of these materials. Copyright © 2012 John Wiley & Sons, Ltd.