Bulk Heterojunction Solar Cells: Morphology and Performance Relationships

The importance of the film morphology is implied by the number of extensive structural characterization techniques, which have been developed and carried out on BHJ films. Key techniques include X-ray scattering and various forms of electron microscopies and scanning probe microscopies. It is also evident that the BHJ morphology can be modified by the molecular structure of the blend components and the processing conditions, including choice of solvent and solvent additives, thermal annealing, and other postdeposition treatments such as polar solvent treatment, insertion of a conjugated polyelectrolyte as an interlayer between the active layer and electrode. Special emphasis is placed on the detailed morphology, characterized by the different techniques employed so far, of the active layer after different processing approaches.