Spin-Exchange and Energy Transfer at Hybrid Molecular/Lanthanide Nanoparticle Interfaces to Control Triplet Excitons

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SPICE will deliver a new paradigm for the control of spin-1 triplet excitons. The starting point for SPICE is our recent discovery that in hybrid systems of organic semiconductors and lanthanide-doped inorganic nanoparticles it is possible to spin-exchange couple the molecular spin to the unpaired spins on the Ln3+ ions and to transfer energy from triplet excitons to Ln3+ and vice versa (Han et al., Nature 2020). This opens a fascinating area for exploration and discovery, as well as routes to control triplet dynamics in ways not possible via current methods.SPICE will combine steady-state and ultrafast optical spectroscopy with molecular and lanthanide nanoparticle design to explore these new phenomena and build a comprehensive mechanistic understanding of spin- exchange coupling and energy transfer at the organic-lanthanide nanoparticle interface and make proof of concept demonstrations of novel materials and device functionalities. Key aims will be:1) Building structure-function relationships to understand the mechanisms of:(a) spin-exchange mediated brightening of the normally forbidden S0-Tn transitions; (b) spin-exchange mediated enhancement of intersystem crossing (S1-T1) rates; (c) energy transfer from triplet excitons to Ln3+ and vice versa; (d) the triplet-Ln fusion process (T1+Ln-S1) to give upconverted emission and the hybrid Ln-Organic electronic states that must mediate this process.2) We will then use the insights generated to develop new materials with optimised energy transfer and emission properties.3) Finally, we will make proof of demonstrations of LEDs and optically pumped lasers with NIR emission (1300-1600nm) and NIR to blue upconversion at very low excitation powers that can trigger chemical reactions in biological environments.The success of SPICE would open new avenues to harness triplet excitons that could find transformative applications in areas ranging from photocatalysis and optoelectronics to 3D printing and optogenetics.