Green, James D.;
(2025)
Advances in Rapid Calculation of Electronically Excited States.
Doctoral thesis (Ph.D), UCL (University College London).
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Abstract
With the recent popularity of OLEDs for display technologies, the ever increasing need for both indoor and outdoor photovoltaics and the rise of quantum computing, understanding electronically excited states in organic molecules has never been more relevant. Computing excited states is a well-known challenge, and while many methods for such calculations exist, they are generally very computationally expensive. Meanwhile, there is a growing interest in high-throughput workflows and AI, which requires methods for rapid and on-the-fly calculations. This prompts efforts towards faster and more computationally efficient methods for calculating excited states. Moreover, the design of functional molecules tailored for applications such as optoelectronics, whether by AI, screening or otherwise, requires excited state intuition at the outset, hence requiring continued endeavours to unify the theories of electronically excited states and provide intuitive design rules. This thesis addresses both of these challenges. Firstly, an inverse design approach for chromophores utilising perturbation theory is proposed, and design rules are derived, with the aim of forming a pre-screening method for chromophores. Attention is then turned to the computational challenge of radicals, where a spin-pure rapid-screening method for their electronic spectra is proposed and found to be as accurate as much more computationally demanding methods. This method is further extended to organic radicals containing heteroatoms by learning the optimal parameters from their experimental UV-Visible spectra. Finally, a long-lasting gap in the electronic structure theory of alterant hydrocarbons is filled by deriving pseudoparity selection rules for alternant hydrocarbon radicals. Using newly-derived theory and computational calculations, many previously observed spectroscopic properties of radicals are explained in a unified way. The computational methods and theories presented here aim to accelerate the design of molecules for optoelectronic applications, and beyond.
| Type: | Thesis (Doctoral) |
|---|---|
| Qualification: | Ph.D |
| Title: | Advances in Rapid Calculation of Electronically Excited States |
| Open access status: | An open access version is available from UCL Discovery |
| Language: | English |
| Additional information: | Copyright © The Author 2025. Original content in this thesis is licensed under the terms of the Creative Commons Attribution 4.0 International (CC BY 4.0) Licence (https://creativecommons.org/licenses/by/4.0/). Any third-party copyright material present remains the property of its respective owner(s) and is licensed under its existing terms. |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Chemistry |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10214052 |
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