title: Synthesis of donor-acceptor orthogonal molecular structures for optimised thermally activated delayed fluorescence
Creators: name: Vybornyi, Oleh
Publisher: name: University of Glasgow
Year: 2019
Subjects: subject: Organic chemistry, synthesis, organic electronics, organic light-emitting diode, thermally activated delayed fluorescence, scale-up, naphthalimide, photophysics.

description: In general, this thesis summarises all the work which had been done over the past three years of my PhD from December 2015 to December 2018. The presented work is the result of the fruitful collaborations with other partners from the European Union-funded Marie Skłodowska-Curie project EXCILIGHT. The main purpose of the project is to train young researchers to tackle important scientific questions and make a valuable contribution to the field of organic electronics. In particular, the aim of our consortium is to contribute knowledge into the understanding of the working principle of organic light-emitting diodes, by producing a set of new organic materials and then to utilize them in optoelectronic devices for further study. A number of fundamental problems related to the device performance, such as efficiency and stability must be studied and overcome for successful penetration of next generation technologies into the consumer market. The present thesis shines light upon all the novelties in organic electronics research and is divided into five chapters for a better tracking of a transition from the fundamental theoretical properties to experimental solutions. The major part of this thesis is devoted to the theoretical background of organic semiconductors, systematization of a chemical design, synthesis and characterization of novel donor-acceptor compounds. The first chapter of the thesis is an introduction and overview of the real-life optoelectronic applications of organic materials, for example in photovoltaic, semiconducting and lighting technologies. A brief historical introduction is given for all three main applications of organic materials, followed by the demonstration of the device structure and working principle of organic photovoltaics and field-effect transistors. The majority of the chapter is dedicated to the up-to-date overview of organic light-emitting diodes: the history of their development, working principle, main applications, list of commercial products as well as a summary of undeniable advantages and set of current disadvantages. The second chapter is as a comprehensive overview of the electronic structure, chemical composition and the idea behind synthetic engineering of the compounds suitable for organic electronics. A big emphasis was made on the explanation of the Jablonski diagram and all the photophysical processes inside organic compounds including absorption, emission and nonradiative decays. On the basis of Jablonski diagram, the thermally activated delayed fluorescence phenomenon was discussed with further explanation why it is such an important technique for the improvement of OLED efficiency. In the third chapter the utility of the Buchwald-Hartwig reaction and its application in the synthesis of the highly efficient TADF emitters is described. I present a method towards a gram-scale synthesis of new materials starting from commercially available compounds which can be transformed into compounds with unique optoelectronic properties. Different synthetic techniques are described for successful preparation of the materials. In addition, a brief overview of OLED devices based on these emitters have been shown. The fourth chapter represents a brand-new way to synthesize tetrazine-based donor-acceptor compounds. In addition, the successful utilisation of the prepared compounds have been involved in the Diels-Alder [4+2] cycloaddition which is of high importance in the field of bioconjugate chemistry for the delivery, labeling and targeting of biomolecules such as proteins, lipids, antibodies etc. The fifth chapter is solely dedicated to the synthesis of the new naphthalimide-containing donor-acceptor molecules. Also, structural isomers of the prepared compounds are reported for the first time in the literature. In addition to the synthesis of the new materials, their crystal structure and photophysical properties are also reported. A comprehensive analysis of the photophysical properties was conducting in the molecules bearing different donor units as well as between two structural isomers. At the end of the thesis, a general outlook and future prospective of organic electronics are summarized.