Synthesis and characterisation of low band gap polymers for organic photovoltaics and transistors

摘要

The replacement of silicon as a semiconductor within photovoltaics and transistors is key to producing cheaper and easier to produce devices, which can go some way towards tackling global issues such as global warming. Organic electronics have many advantages over silicon due to the fact that they can be solution processed, are cheap and can be deposited on flexible substrates. However, current efficiencies of organics photovoltaics (OPVs) and transistors (OFETs) are lagging behind those based on inorganic materials and thus the development of new materials will be the focus of this thesis.ududThe first part of this thesis is devoted to the synthesis of a novel fused hexacyclic thiophene donor molecule, 4T with the primary aim of producing a novel copolymer for OPVs and OFETs. A variety of synthetic routes are explored to produce the desired 4T monomer with the final outcome being the production and characterisation of the novel copolymer P4T-BT.ududThe next section incorporates the development of more environmentally friendly novel phenyl isoindigo copolymers which show high efficiencies in OPVs and OFETS. Further modification of the isoindigo core produced a novel thiophene isoindigo monomer, which improved the planarity of the copolymers subsequently synthesised. These copolymers had substantially lower band gaps than the analogous Phenyl isoindigo copolymers that were synthesised for comparison. Random terpolymers of the thiophene and phenyl isoindigo monomers were subsequently synthesised to incorporate the properties of the two monomers into one polymer, in order to broaden the spectral absorption of the polymers. Further attempts to produce thiazole isoindigo and furan isoindigo are also outlined in this section.ududThe third part of this work explores the development of polymers based on Pechmann dyes for application in OFET devices.