Miscibility, Crystallinity, and Phase Development in P3HT/PCBM Solar Cells: Toward an Enlightened Understanding of Device Morphology and Stability

Rapid improvements in organic solar cell efficiency have brought these devices into the spotlight as a potential source of abundant electricity. Despite much empirical progress, fundamental understanding is still lacking. Due to the required three-dimentional nanoscale morphology, determining structure–performance relationships has been a major challenge, and a convergent understanding has yet to emerge. We discuss recent major advances in delineating the characteristics of the most common organic solar cells. The large variations in device performance reported, the contradictory morphologies observed, and the determination of the underlying driving forces need to be resolved. Deeper understanding that can provide a roadmap to improved devices will only occur through refined consideration of material characteristics and fabrication procedures in conjunction with increased use of advanced characterization. We additionally highlight the recently discovered partial miscibility of the component materials, its influence on device processing and lifetime, and its emergance as an important indicator of stability.