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Title: Heteroatom and bridged-ring π-conjugated polymers and their use in organic electronics
Author: Hurhangee, Michael
ISNI:       0000 0004 7969 8033
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2018
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Organic semiconductors have attracted much interest over the last two decades for their potential to replace inorganic semiconductors in a range of applications. This work focuses on the design, synthesis, analysis and characterisation of new semiconducting polymers, and their use as the semiconducting layer in organic field effect transistors. This thesis reports and analyses fourteen novel semiconducting polymers. The substitution of thiophene for thiazole and has led to the synthesis and characterisation of isostructural thiazole containing polymers. We have observed that thiazole can induce extra crystallinity and molecular ordering, but have also noted that thiazole incorporation can lead to increased instability and disorder in polymers. The substitution of protons for fluorines has led to isostructural fluorinated polymers. We have observed that fluorination can stabilise energy levels and does not significantly impact disorder, the solid-state or optical properties. But fluorination does have an adverse impact on the charge transport properties. Through the synthesis of IDT-BT and other IDT copolymers, we have developed an understanding of how molecular design, purification, and annealing can affect its preferential disorder and morphological properties. Furthermore, we have the developed the idea that charge-transport along the rigid planar backbone of IDT-BT is a major charge transport pathway, and that by extending the bridged IDT motif with fused rings we could enforce even greater rigidity and planarity and reduce alkyl chain density along the polymer backbone. The idea increasing the bridge donor length has culminated with the synthesis of TIF. TIF-BT has achieved high charge carrier mobilities and high on-currents of 3.0 cm2 V-1 s-1 and 0.8 mA, respectively. TIF-BT was judiciously designed through applying molecular design criteria, which have been developed throughout this work by improving increasing our understanding of the relationship between chemical structure and charge-transport.
Supervisor: McCulloch, Iain Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral