Dye-sensitized TiO2 thin-film solar cell research at the National Renewable Energy Laboratory (NREL)

The idea of dye-sensitization of inorganic materials has been around for a long time, and a vast amount of literature exists on this subject. The first studies of photoelectrochemical effects in dye-sensitized TiO2 for solar energy conversion were carried out by Deb et al. (Unpublished Report on Project SECSC (Solar Energy Convertion and Storage cell) Optel Corporation, Princeton, NJ, 1975–76), in the mid-1970s. A breakthrough occurred in recent years when Graetzel (Nature 414 (2001) 338) reported a photoelectrochemical solar cell in which a thin film based on nanoparticles of TiO2 was sensitized by a more efficient and stable dye system based on Ru(11)-complexes. Some of the key research issues that are currently being addressed at NREL include: device fabrication and characterization, role of structural properties of TiO2, electron transfer processes, novel ideas on dye-sensitization and light harvesting, and applications in optoelectronic devices. The current status and future direction of research and technology development are discussed.