The synthesis and analysis of polymers and small molecules for use in organic electronics

Organic Semiconducting materials (OSCs) are integral to the next generation of devices such as flexible screens and solar panels, thanks to their flexible, solution processable and synthetically cheap nature. Although the field of OSCs has moved forward rapidly in the last decade, further research must be conducted to improve performance and efficiencies so as to be competitive with current silicon technologies whilst opening up new markets. One method of improving the current technology is through the chemical modification of these materials to tune their parameters whether this is optical, energetic or morphological. In this thesis, we report the complex synthesis of new thiazole based polymers for use in organic field effect transistors (OFETs) and organic photovoltaics (OPV) with exceptional planarity through a ‘conformational lock’ between the thiazole and thiophene units. Although these polymers performed poorly in OPV and OFET, their interesting properties give new insight into thiazole based polymers, whilst also showing a novel ring closure reaction previously unpublished. This thesis also reports on the synthesis of new diketopyrrolopyrrole polymers with electron rich flanking units used to form strong push-pull hybridisation across the backbone to create low band gap, near-IR absorbing materials. The high molecular weight pDTP-DPP-TT behaveds in a rod like manner due to a ‘hydrogen-bond’ bond-like’ interaction between the DPP core and the DTP flanking unit. This results in exceptionally high extinction coefficients – a prerequisite for high currents in OPV devices. Finally, the thesis reports on the extension of the XBR family with the addition of two new non-fullerene acceptor materials CBR and CBI. The use of non-fullerene acceptors in OPV should not only heavily bring down the materials cost of devices, but also open up new absorption pathways to allow greater device efficiencies. This work looked into how chemical modifications of the central core and flanking units can be used to tune the electronic energy levels, as well as the optoelectronic properties of the materials both individually and in devices.Open Acces