Characterization of the mesoscopic structure in the photoactive layer of organic solar cells: A focused review

Organic photovoltaics (OPVs) belong to a class of devices where the nanometer scale morphology of the active layer has a large impact on device performance. However, characterization of the morphology of organic semiconductor mixtures that make up the active layer of OPVs remains a challenge. Here, the characterization methods that can be used to quantitatively and qualitatively measure the mesoscopic structure of the active layer in organic solar cells are described. Specifically, we focus on the use of X-ray and neutron scattering, scanning probe microscopy, and electron and X-ray microscopy for morphological characterization of organic semiconductor mixtures at mesoscopic length scales.

► We examine the various techniques used in the morphological characterization of the active layer of organic solar cells.
► The combination of microscopy and scattering is important to develop a complete quantitative picture of the mesoscopic structure of organic semiconductor mixtures.
► Energy-filtered transmission electron microscopy can be used to create maps of the local composition of organic semiconductor mixtures.
► Small angle scattering data of the active layer of polythiophene/fullerene solar cells are dominated by the structure factor.