The dwindling supply of fossil fuels exposes the need to develop efficient methodologies for renewable energy harvesting. Photon upconversion via sensitized triplet-triplet annihilation (TTA-UC) is a method for transforming low-power, non-coherent radiation into photons of higher energies. While well-established in solution, TTA-UC is significantly more challenging to achieve in solid materials due to limitations in exciton mobility – requiring advanced design strategies to mitigate aggregation of sensitizer and annihilator dye-pairs at high loadings. Covalent attachment of chromophores to polymer backbones has improved upconversion quantum yield compared to blends. However, overall upconversion efficiency is still limited due to diffusion-enhanced back-energy transfer (back-ET) to the sensitizer. Here we synthesized a library to examine the effect of attachment versus blending of the palladium (II) octaethylporphyrin (PdOEP) and diphenylanthracene upconverting pair. We implemented a novel anthracene singlet sink intended to prevent back-ET. Methacrylate-based copolymers were synthesized by reversible addition-fragmentation chain-transfer polymerization using a PdOEP-like bifunctional chain-transfer agent. Sequential addition of chromophore-functionalized methacrylates affords better control towards the preferred radii for exciton transport. Photophysical characterization was performed in solution and the solid state to elucidate the role of sequence control on diffusion kinetics. Additionally, we studied how the introduction of a singlet sink changed upconversion quantum yield. Our strategy promotes efficient TTA-UC in glassy thin films through implementation of a novel three-part chromophore system - limiting unwanted back-ET and promoting favorable ordering towards more efficient exciton transport.

Towards high efficiency sensitized triplet-triplet annihilation in glassy copolymer systems

ACS Fall 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.