Thermally activated delayed fluorescence in an optically accessed soft matter environment

Abstract

Organic material compositions, able to demonstrate bright delayed fluorescence either by electrical excitation or by optical excitation, are being applied in various fields of research ranging from sunlight-powered photonic devices and organic light emitting diodes, to real-time minimally invasive thermometry and/or oximetry in cell-cultures. This review will provide extensive discussion on the influence of thermal phenomena on organic material compositions that demonstrate effective delayed fluorescence. In particular, emphasis will be placed on the technological flexibility of different approaches together with examples and prospects of their applications and optimization strategies. In particular, for the triplet–triplet annihilation photon energy upconversion devices, oxygen quenching and/or local temperature increase represent serious issues, minimizing the photon flux obtained and leading to the acceleration of device aging. However, such types of delayed fluorescence photonic applications, based on optically excited triplet states, are much more sensitive to tiny variations of the sample temperature and local concentration of molecular oxygen. To fully exploit the enormous application potential of delayed fluorescence based technologies, a deep understanding of the impact of the thermal phenomena on the aging properties and photonic efficiency is necessary. Such a ‘guide’ for designing robust delayed fluorescence based photonic materials with low sensitivity towards deactivation by atmospheric oxygen and temperature variations will be helpful for researchers working in fields, such as photo catalysis, organic solar cells, organic upconversion displays, minimally-invasive life-science sensing, molecular solar fuels etc.