In the push to develop artificial photosynthesis, researchers have been working to understand fundamental photochemical processes. Aleksandr Avramenko and Aaron Rury comprehensively studied how the dynamics of model light harvesting molecules is affected by the formation cavity polariton states, hybrid states of light and matter.
Using two well-studied chromophores – tetraphenyl porphyrin molecules with zinc or copper at their cores – the authors monitored how strong coupling to photons in tiny two-mirror cavity systems affected the molecules’ excited state dynamics. The authors used both standard spectroscopic analyses to understand the static electronic structure of the system and ultrafast laser measurements to study the dynamics directly on timescales of just a trillionth of a second.
The results showed that increasing the number of cavity molecules increased light-matter coupling. Surprisingly, in the case of zinc tetraphenyl porphyrin, he results also showed energy dissipated faster from the delocalized upper polariton state to the excited states of molecules localized within the cavity structure. Using simple kinetic models, the authors concluded that vibrations of these model light harvesting molecules play a significant role in controlling the excited state dynamics of polaritons.
“We found good agreement between the two methodologies,” said Rury. “It turns out you don’t need a half a million-dollar laser system to do this type of analysis.”
The authors hope to extend their two-measurement method to build a large catalogue of different molecular samples. They hope such a catalogue can be used by other researchers who will only need simple spectroscopic measurements to understand the dynamics of a molecule. Eventually, this work could even help make solar cells more efficient.
Source: “Local molecular probes of ultrafast relaxation channels in strongly coupled metalloporphyrin-cavity systems,” by Aleksandr G. Avramenko, and Aaron S. Rury, Journal of Chemical Physics (2021). The article can be accessed at https://doi.org/10.1063/5.0055296.
This paper is part of the Polariton Chemistry: Molecules in Cavities and Plasmonic Media Collection, learn more here.
