Nano-scale Morphology for Bulk Heterojunction Polymer Solar Cells

In any high performance polymer solar cell, the morphology is always an important aspect. The bulk-heterojunction morphology is a challenging research area, which is the focus of this chapter. Many characterization techniques have been used to investigate the BHJ morphologies of active layers in OPVs; which can be classified into reciprocal-space and real-space techniques. We will discuss both the reciprocal-space techniques generally used to obtain spatially averaged information (X-ray or neutron scattering), as well as real-space techniques for analyzing the phase separation and aggregation of BHJ morphology. Our focus will be on how X-ray scattering and transmission electron microscopy based characterization techniques can be used to analyze the effects of the relative length scales of PCBM clusters and polymer (P3HT as example) crystallites on device performance.