DNA Directed Organic Semiconductor Interactions Controlling Excitons, Charge Transfer States, and Singlet Fission

Excited states in organic semiconductors are generated, transported, and converted through π-orbital interactions between multiple molecules. Hence, efficiency depends on the relative geometries between molecules. Yet, control over spatial assembly of organic semiconductors is challenging. Large aromatic molecules will self-assemble into extended structures with no size or positional control. Deterministic interactions between two different semiconductor molecules is even rarer. In contrast, selective and high-yielding DNA base pairing interactions can control discrete, self-assembly of nanoscale structures. After introducing relevant synthetic and theoretical background to DNA assembly and interchromophore coupling, the synthesis of DNA-conjugated organic semiconductors are described. Semiconductors were inserted into the phosphodiester backbone of DNA, maintaining DNA’s self-assembling properties. The appended DNA direct the interactions between predefined numbers of the same molecule, followed by hetero-assemblies composed of different molecular backbones. DNA-directed changes are interrogated by excitonic couplings, using steady-state time-resolved optical spectroscopy to track the excited state evolution. Homo-aggregate molecules exhibit excitonic coupling. In contrast, heterostacks were capable of charge transfer between an electron-donor and electron-acceptor on DNA. Finally, singlet-fission active molecules were attached to DNA. This process generates two triplet excitons from one singlet exciton. The evolution of this process was tracked using time-resolved optical and magnetic spectroscopy. The combined observations in this thesis show multi-chromophore dependent phenomena are replicated in the aqueous DNA environment. Importantly, DNA successfully restricts and controls the extent of chromophore interaction to produce size-dependent phenomena and impart spatial control of multiple, different semiconductors.

Name dc:type.qualificationname

Doctor of Philosophy (PhD)

Level dc:type.qualificationlevel

Doctoral

Grantor dc:publisher.institution

University of Cambridge

Year dc:date.issued

2020

Author dc:creator

• Gorman, Jeffrey

Advisor dc:contributor.advisor

• Friend, Richard

• DNA
• Singlet Fission
• Organic Semiconductor
• Charge Separation
• Excitonic Coupling
• Self Assembly

Licence

• https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/0c03bbf1-a51d-486b-a6f5-fac0f3947d41/download
• https://www.rioxx.net/licenses/all-rights-reserved/

Language dc:language

eng

Author Identifier

0000-0002-6888-7838
0000-0001-6565-6308

OAI identifier oai:identifier

oai:www.repository.cam.ac.uk:1810/313457