Organic Liquids in Energy Systems

This chapter introduces a new perspective of functional organic liquids toward the application to photon energy storage and conversion, by highlighting two intriguing functions: the molecular solar thermal fuels and photon upconversion (UC). In both topics, it is of importance to maximize the unique potential of π-liquids. Room-temperature ionic liquids (ILs) have been attracting much interest as environmentally benign solvents for a variety of applications because of their unique properties including their very low vapor pressure and high ionic conductivity. Their applications include the media for organic chemical reactions, separations, and electrochemical and energy applications. Photon UC through annihilation between two long-lifetime excited triplets, namely, the sensitized triplet-triplet annihilation-based photon UC, has recently come into the spotlight because of its wide applications that range from renewable energy production to bioimaging and phototherapy.