One of the major challenges in developing electrochemical devices for energy generation has been the identification and development of materials with outstanding performance at reduced (intermediate) temperatures (500-700 degrees C), increasing the durability and lowering the cost of the device. A solid-state electrochemical cell is in outline a simple device consisting of three components: anode, electrolyte and cathode. The function of each component is critical to cell performance, and as interest in fuel cells and electrolysers has gathered pace, many materials have been evaluated as functional components of these cells. Typically, the requirement for new materials development has been the drive to lower operation temperature, overcoming sluggish reaction kinetics in existing materials. Novel materials for the functional components of both electrolysers and fuel cells are introduced, with emphasis placed on the air electrode and electrolyte, with the potential of new classes of materials discussed, including layered materials, defect fluorites and tetrahedrally coordinated phases. Furthermore, the opportunity presented by thin film deposition to characterize anisotropic transport in materials and develop devices based on thin films is discussed.