Novel Intramolecular Charge Transfer Materials and their Optoelectronic Properties

Abstract

Abstract
Novel Intramolecular Charge Transfer Materials and their Optoelectronic Properties
Kathryn Clare Moss, Durham University, 2012

A summary of aspects of the literature surrounding organic donor-acceptor systems for a variety of optoelectronic applications (OLEDs, OFETs, OPVs) is presented with a particular focus on two key moieties; 9,9-dialkylfluorene (F) and dibenzothiophene-S,S-dioxide (S). The development of these “building blocks” into novel systems capable of intramolecular charge transfer, i.e. donor-acceptor containing materials, is then discussed.

The syntheses and photophysics of a number of novel fluorescent ambipolar trimers based on F and/or S are presented which allow investigations to be performed into the excited state behaviour of the systems. Tuning of the emission colour is demonstrated from deep blue to green by varying the strength of the donor and/or by manipulating the extent of conjugation through the systems. Related trimers are investigated which exhibit the unusual phenomenon of (low temperature) phosphorescence from all-organic systems. Development of the F/S trimers into polymers gives systems which are capable of emitting white light and all-fluorescent white-emitting devices are presented.

Following on from this, the use of F as a molecular bridge between donor (ferrocene) and acceptor (C60) moieties is presented, with the aim of modulating charge transfer between the two by varying the linker between ferrocene and F as well as the length of the fluorene bridge. The synthesis and electrochemical behaviour of the compounds is discussed and photophysical studies are currently being undertaken.

Finally, random co-polymers of F, S and related analogues are presented to investigate the morphology of such systems with regard to beta phase formation. A number of F and/or S based systems are also presented with the aim of finding novel high triplet energy host materials for OLEDs. The syntheses and photophysical studies of these materials are discussed.

Overall, the work demonstrates the great potential of F and S in donor-acceptor systems for a wide variety of optoelectronic applications.