Singlet Fission in Carotenoid Aggregates (SIFICA)
Lead Research Organisation:
University of Oxford
Department Name: Oxford Chemistry
Abstract
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Organisations
People |
ORCID iD |
| William Barford (Principal Investigator) |
Publications
Barford W
(2021)
Measuring time-dependent induced quantum coherences via two-dimensional coherence spectroscopy
in Physical Review A
Manawadu D
(2022)
Singlet Triplet-Pair Production and Possible Singlet-Fission in Carotenoids.
in The journal of physical chemistry letters
Marcus M
(2020)
Triplet-triplet decoherence in singlet fission
in Physical Review B
Valentine D
(2020)
Higher-energy triplet-pair states in polyenes and their role in intramolecular singlet fission
in Physical Review B
| Description | 1. Singlet Triplet-Pair Production in Carotenoids Internal conversion from the photoexcited state to a correlated singlet triplet-pair state is believed to be the precursor of singlet fission in carotenoids. We developed numerical simulations of this process using a pi-electron model that fully accounts for electron-electron interactions and electron-nuclear coupling. The time-evolution of the electrons is determined rigorously using the time-dependent density matrix renormalization group method, while the nuclei are evolved via the Ehrenfest equations of motion. This method was applied to zeaxanthin, a carotenoid chain with 18 fully-conjugated carbon atoms [1]. The simulated dynamics shows that the internal conversion of the primary photoexcited state, S2, to the singlet triplet-pair state occurs adiabatically via an avoided crossing within ca. 50 fs, with a yield of ca. 60%. [1] Singlet triplet-pair production and possible singlet-fission in carotenoids, D. Manawadu, D. J. Valentine, M. Marcus and W. Barford, J. Phys. Chem. Lett. 13, 1344 (2022) 2. Triplet-Triplet Decoherence in Singlet Fission Singlet fission is commonly defined to involve a process in which an overall singlet state with local triplet structure spin-decoheres into two triplet states, therefore completing the fission process commonly observed in pi-conjugated systems, such as carotenoids and acenes. This process, often defined in loose terms involving the multiplicity of the overall state, was investigated using a uniform Heisenberg spin-chain subjected to a dephasing environmental interaction. We introduced new results from quantum information theory which allows for the quantification of coherence and entanglement in a bi- and multipartite system. The calculated measures on these quantum effects can be linked to observables, such as magnetisation and total spin, both with simulations of the model and using theoretical methods. We demonstrated that these observables can act as a proxy for the coherence and entanglement measures and the decay of both of these between the two local triplets can be monitored, enabling a clear definition of the spin-decoherence process in singlet fission. These results are applicable to carotenoids. [2] Triplet-triplet decoherence in singlet fission, M. Marcus and W. Barford, Phys Rev B 102, 035134 (2020) |
| Exploitation Route | By experimentalists, to interpret their singlet fission results. By technology, to increase the quantum efficiency of photovoltaic devices. |
| Sectors | Energy |