Multiscale modelling of charge and energy transfer in molecular solar cells and photosystems
File(s)
Author(s)
García Medranda, Daniel
Type
Thesis
Abstract
Charge photogeneration in natural and artificial organic photosystems share similar principles, involving light absorption, exciton diffusion, charge transfer, separation, and recombination, which collectively determine light-to-energy conversion efficiency. However, structural differences between the two systems lead to distinct limitations. In organic solar cells, most losses arise from non-radiative charge recombination at large donor-acceptor interfaces. In contrast, natural photosystems confine charge separation to a small reaction centre with only a few pigments. This structure reduces non-radiative losses but introduces limitations in the kinetics of charge transfer, particularly under high light intensities.
In this thesis, we study the charge separation process in both types of systems by a unified theoretical model, attending to their molecular structure. We coarse-grain the system to build a tight-binding Hamiltonian considering the molecular interactions. This approach provides a description of the system’s excited states, accounting for extended excitons and charge transfer states. By analysing the evolution of these excited states, we evaluate the yield of excitation recombination and energy storage, enabling to quantify the energy conversion efficiency of the system as a function of its structural and chemical properties.
Overall, this thesis presents a model to explore the correlation between the chemical and microstructural properties of molecular energy converters and their efficiency and losses. This work advances our understanding of how molecular structure and interactions shape the performance of molecular energy conversion systems.
In this thesis, we study the charge separation process in both types of systems by a unified theoretical model, attending to their molecular structure. We coarse-grain the system to build a tight-binding Hamiltonian considering the molecular interactions. This approach provides a description of the system’s excited states, accounting for extended excitons and charge transfer states. By analysing the evolution of these excited states, we evaluate the yield of excitation recombination and energy storage, enabling to quantify the energy conversion efficiency of the system as a function of its structural and chemical properties.
Overall, this thesis presents a model to explore the correlation between the chemical and microstructural properties of molecular energy converters and their efficiency and losses. This work advances our understanding of how molecular structure and interactions shape the performance of molecular energy conversion systems.
Version
Open Access
Date Issued
2025-01-10
Date Awarded
01/08/2025
License URL
Advisor
Nelson, Jenny
Sponsor
European Research Council
Grant Number
742708
Publisher Department
Department of Physics
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)