Triplet excitons are important because their long lifetimes provide a versatile excited-state reservoir for efficient energy harvesting, storage and transfer, long-lived light emission in organic materials. Our research focuses on harnessing, stabilizing and utilization of triplet excitons in purely organic materials. We employ diverse covalent and non-covalent strategies to bias the emission pathways and fine tune the spectral characteristics. The following are some of the approaches used by us towards achieving ambient triplets in challenging conditions, including aqueous environments, extending the use of triplet mediated processes in water.
4A) Phosphorescence in Aqueous Phase via Supramolecular Scaffolding:
Triplet stabilization has been a challenging task. We have employed a supramolecular scaffolding approach by using the co-assembly of organic phosphors with an inorganic silicate template to minimize vibrational quenching of triplet excitons. Long-lived triplet excitons provide a persistent energy reservoir that enables controlled energy transfer, triplet harvesting, and long-lived emission. This supramolecular confinement effectively modulates the excited-state dynamics and prolongs the lifetime of the triplet states. Such stabilized triplets can further serve as efficient energy donors for sensitizing other chromophores and accessing otherwise difficult-to-achieve excited-state pathways.
4B) Biasing the Excited State by Covalent / Non-Covalent Approaches:
Engineering the electronic excited state manifolds of organic molecules can give rise to various functional outcomes, including ambient triplet harvesting. We employ diverse covalent and non-covalent strategies to bias the emission pathways and fine tune the emission colour. This enables a wide-range phosphorescence and delayed fluorescence spanning across the visible spectrum.
4C) Circularly Polarized Phosphorescence and Delayed Fluorescence:
Achieving efficient circularly polarized luminescence (CPL) with a high luminescence dissymmetry factor (|glum|) in purely organic systems is a vibrant and rapidly evolving field of research. We employ non-covalent design strategies for the tuning of emission from the orange to deep-red regions by incorporating various donors. We are currently investigating chiral scaffolds containing our phosphors to achieve efficient circularly polarized phosphorescence and delayed fluorescence.
