Figure 13.

Schematic of various types of device architectures of solar cells. Red domains correspond to electron donor phases, while blue domains correspond to electron acceptor phases (a) Single-layer device, sandwiched between electrodes with different work functions; (b) bilayer device, with increased efficiency due to exciton dissociation occurring at the interface between phases; (c) bulk heterojunction device, where domain size is close to the exciton diffusion length of around 10 nm; (d) A proposed ideal film morphology, and ordered bulk heterojunction device where electrons and holes always have pathways to their respective electrodes. Reproduced from [72] with permission of the Royal Society of Chemistry.