Protective Strategies Toward Long-Term Operation of Annihilation Photon Energy Upconversion

Abstract

The process of triplet-triplet annihilation photon energy upconversion (TTA-UC) performed in soft-matter environment relays on optically created densely populated organic triplet ensembles. In soft-matter matrix, it is a diffusion-controlled process, simultaneously demonstrating essential dependences on the environmental parameters such as matrix temperature, matrix viscosity, and presence of molecular oxygen, dissolved into the solvent or adsorbed on the polymer film. It is important to notice that all these environmental parameters are strongly interrelated and their impact on the temporal evolution of the densely populated triplet ensembles is not a linear combination of its partial impacts. If the TTA-UC process is applied toward solar energy storage and/or conversion technologies, the influence of the singlet oxygen generation generally leads to lower quantum yield (QY) and simultaneously to accelerated aging of the upconversion device. The generation of singlet oxygen is much more harmful for the studied object, if the process of TTA-UC is used as a sensing mechanism for probing of the local temperature/local oxygen content in cell cultures. In this chapter, the development of an effective protection strategy against quenching by molecular oxygen and protection against the subsequent photooxidation caused by singlet oxygen is discussed.