Functional blends of organic materials for optoelectronic applications

Abstract Optoelectronic materials are employed in devices where light is used to affect electronic processes in materials (or vice versa) and thus provide a useful functionality. Devices that belong to this category include solar cells, light-emitting diodes (LEDs), light-emitting transistors (LETs), and photodetectors. Often, however, not only one material is used in these devices, but quite a few. The purpose of this chapter is to discuss blends of organic materials that play an important role in optoelectronic devices. The key processes and concepts in the thermodynamics and kinetics of mixing are reviewed, including materials phase behavior and the resulting morphology, both of which affect the optical and electronic properties of devices. When multiple materials are combined into a single device, many potential sources of failure may arise from the mutual incompatibility of device components or instability under device fabrication/operation conditions. Therefore, proper identification of potential materials for high-performing devices has great importance. Specific applications in which such blends are employed will be the main focus of the discussion. Particular attention will be paid to the structure-property relations that enable their compatibility in the blends and good device performance.