Singlet fission in carotenoids
Lead Research Organisation:
University of Oxford
Department Name: Theory and Modelling in Chem Sci CDT
Abstract
EPSRC Classification: Computational & Theoretical Chemistry
Singlet fission in carotenoids
Absorption of photons in molecules cause electronic excitations. The excited electron leaves behind a positively charged hole, and the electrostatic interaction between the two forms a bound state, termed an exciton. The process of electronic excitation conserves spin, and therefore forms a (S=0) singlet photoexcited state.
In conjugated organic molecules like polyenes and polyacenes, thus formed excitons can undergo singlet fission. Singlet fission is a mechanism whereby a photoexcited spin singlet (S = 0) exciton dissociates into a pair of triplet (S = 1) excitons. This translates to exciting two electrons in the molecule, and therefore the process is believed to increase the efficiency of photovoltaic devices.
In this project, we aim to do the following. Firstly, we will model the time evolution of the photoexcited singlet state using carotenoids as our model system. The time-dependent density matrix renormalization group technique, along with Ehrenfest equations of motion will be used to evaluate the wavefunction of the system and its changes with time. Density matrix renormalization group technique is a numerical technique used to evaluate wavefunctions of strongly correlated quasi one-dimensional systems based on minimizing the loss of information of the system. Initially, we treat the nuclei as classical coordinates in the classical Ehrenfest dynamics implementation, and then we will introduce quantum fluctuations to the nuclei, aiming for a better representation of the real system.
The triplet pair formed via singlet fission is highly correlated at the instance of its formation. Subsequent interactions with the environment are capable of causing loss of coherence. The second aim of this project is to model this triplet decoherence process.
With the knowledge of the wavefunction of the system, it is possible to calculate observables like transient absorption measurements. As the third aim of this project is to calculate such observables and compare the results with experimental observations. This will be performed in collaboration with Professor Jenny Clark at University of Sheffield.
We hope the simulation will help us better understand the singlet fission process, specifically the symmetries of the excited state as it moves from the singlet state to the bound triplet pair and beyond.
This project falls within the EPSRC "Energy" and "Quantum technologies" research areas. It also format part of an EPSRC-funded collaboration with the University of Sheffield on singlet fission in carotenoid aggregates.
Singlet fission in carotenoids
Absorption of photons in molecules cause electronic excitations. The excited electron leaves behind a positively charged hole, and the electrostatic interaction between the two forms a bound state, termed an exciton. The process of electronic excitation conserves spin, and therefore forms a (S=0) singlet photoexcited state.
In conjugated organic molecules like polyenes and polyacenes, thus formed excitons can undergo singlet fission. Singlet fission is a mechanism whereby a photoexcited spin singlet (S = 0) exciton dissociates into a pair of triplet (S = 1) excitons. This translates to exciting two electrons in the molecule, and therefore the process is believed to increase the efficiency of photovoltaic devices.
In this project, we aim to do the following. Firstly, we will model the time evolution of the photoexcited singlet state using carotenoids as our model system. The time-dependent density matrix renormalization group technique, along with Ehrenfest equations of motion will be used to evaluate the wavefunction of the system and its changes with time. Density matrix renormalization group technique is a numerical technique used to evaluate wavefunctions of strongly correlated quasi one-dimensional systems based on minimizing the loss of information of the system. Initially, we treat the nuclei as classical coordinates in the classical Ehrenfest dynamics implementation, and then we will introduce quantum fluctuations to the nuclei, aiming for a better representation of the real system.
The triplet pair formed via singlet fission is highly correlated at the instance of its formation. Subsequent interactions with the environment are capable of causing loss of coherence. The second aim of this project is to model this triplet decoherence process.
With the knowledge of the wavefunction of the system, it is possible to calculate observables like transient absorption measurements. As the third aim of this project is to calculate such observables and compare the results with experimental observations. This will be performed in collaboration with Professor Jenny Clark at University of Sheffield.
We hope the simulation will help us better understand the singlet fission process, specifically the symmetries of the excited state as it moves from the singlet state to the bound triplet pair and beyond.
This project falls within the EPSRC "Energy" and "Quantum technologies" research areas. It also format part of an EPSRC-funded collaboration with the University of Sheffield on singlet fission in carotenoid aggregates.
Planned Impact
Modelling and simulation are playing an increasingly central role in all branches of science, both in Universities and in
industry, partly as a result of increasing computer power and partly through theoretical developments that provide more reliable models. Applications range from modelling chemical reactivity to simulation of hard, glassy, soft and biological materials; and modelling makes a decisive contribution to industry in areas such as drug design and delivery, modelling of reactivity and catalysis, and design of materials for opto-electronics and energy storage.
The UK (and all other leading economies) have recognised the need to invest heavily in High-Performance Computing to maintain economic competitiveness. We will deliver impact by training a generation of students equipped to develop new theoretical models; to provide software ready to leverage advantage from emerging computer architectures; and to pioneer the deployment of theory and modelling to new application domains in the chemical and allied sciences.
Our primary mechanisms for maximizing impact are:
(i) Through continual engagement, from the beginning, with industrial partners and academic colleagues to ensure clarity about their real training needs.
(ii) By ensuring that theory, as well as software and application, forms an integral part of training for all of our students: this is prioritised because the highest quality theoretical research in this area has led to game-changing impacts.
(iii) Through careful construction of a training model that emphasizes the importance of providing robust and sustainable software solutions for long-term application of modelling and simulation to real-world problems.
(iv) By an extensive programme of outreach activities, designed to ensure that the wider UK community derives direct and substantial benefit from our CDT, and that the mechanisms are in place to share best practice.
industry, partly as a result of increasing computer power and partly through theoretical developments that provide more reliable models. Applications range from modelling chemical reactivity to simulation of hard, glassy, soft and biological materials; and modelling makes a decisive contribution to industry in areas such as drug design and delivery, modelling of reactivity and catalysis, and design of materials for opto-electronics and energy storage.
The UK (and all other leading economies) have recognised the need to invest heavily in High-Performance Computing to maintain economic competitiveness. We will deliver impact by training a generation of students equipped to develop new theoretical models; to provide software ready to leverage advantage from emerging computer architectures; and to pioneer the deployment of theory and modelling to new application domains in the chemical and allied sciences.
Our primary mechanisms for maximizing impact are:
(i) Through continual engagement, from the beginning, with industrial partners and academic colleagues to ensure clarity about their real training needs.
(ii) By ensuring that theory, as well as software and application, forms an integral part of training for all of our students: this is prioritised because the highest quality theoretical research in this area has led to game-changing impacts.
(iii) Through careful construction of a training model that emphasizes the importance of providing robust and sustainable software solutions for long-term application of modelling and simulation to real-world problems.
(iv) By an extensive programme of outreach activities, designed to ensure that the wider UK community derives direct and substantial benefit from our CDT, and that the mechanisms are in place to share best practice.
Organisations
People |
ORCID iD |
| David Logan (Primary Supervisor) | |
| Dilhan Manawadu (Student) |