Characterization of the morphology of solution-processed bulk heterojunction organic photovoltaics

Recently, significant advances have been made in understanding and manipulating the morphology of the active layer in bulk heterojunction (BHJ) organic photovoltaic (OPV) devices, due in part, to the development and use of techniques capable of providing detailed information on the spatial distribution and orientation of the components in thin films. Here we review the different types of BHJ composites, their morphological details, the key parameters that dictate the morphology, and an introduction to some of the tools that have been of key importance in these studies. Different materials used to produce BHJ OPVs are summarized, compared and assessed.