ABSTRACT
In this chapter, we review the results of a number of experimental studies that elucidate the nanoscale morphology of the active layer of a polymer : fullerene bulk heterojunction (BHJ) solar cell. In particular, we discuss the growing understanding regarding the role of miscibility that drives phase separation between conjugated polymers and fullerene derivatives. We show that BHJ structures containing phase-separated domains having a characteristic distribution of sizes can be probed using a range of morphological and optical techniques. We then review the methods used to probe and control film morphology, vertical stratification, and structural evolution through modification of film deposition protocol and postdeposition treatments. Finally, we correlate changes in BHJ nanoscale morphology with the optoelectronic properties of organic photovoltaic devices.
