Benzodithiophene containing semiconducting polymers for organic electronics

Conjugated polymers have shown promise as semiconducting materials due to their facile synthesis, tunability of the HOMO and LUMO energy levels, and processibility. Among all classes of conjugated polymers, polythiophenes have shown most promise as semiconducting materials owing to the synthetic control that can be achieved and good electronic properties. Benzodithiophene fused-ring building block is symmetrical, has extended electron delocalization and enhanced planarity. These properties enhance the solid-state packing of the polymers which is crucial for good electronic properties. The ability to functionalize the central benzene core on benzodithiophene offers additional advantages such as tuning the HOMO and LUMO energy levels of the polymers. A broad range of benzodithiophene semiconducting polymers with tunable energy levels and functional groups can be synthesized. Such advantages have generated enormous research interest in the benzodithiophene core as the building block for semiconducting polymers.;Chapter 1 describes the evolution of the field of semiconducting polymers leading to the development of the benzodithiophene core. Synthetic methodologies adopted for the synthesis of benzodithiophene monomers, polymers and their electronic properties are described in this chapter.;Chapter 2 describes the synthesis, characterization, and electronic properties of semiconducting polymers containing benzodithiophene with decylphenylethynyl substituents. A homopolymer and three alternating copolymers have been synthesized and were tested in bulk heterojunction solar cells to investigate the influence of spacing between the side-chains of the polymers on the intercalation of fullerene acceptor (PCBM) between the alkyl side-chains. Additionally, thin-film XRD and TMAFM were used to study the blends of polymers and PCBM.;Chapter 3 describes the synthesis and characterization of donor-acceptor copolymers containing benzodithiophene and various acceptors. Two classes of donor-acceptor copolymers were synthesized; one with benzodithiophene with decylphenylethynyl substituents as the donor unit, second with benzodithiophene with alkylthienyl substituents as the donor unit. The donor-acceptor polymers were tested in bulk heterojunction solar cells and the polymers with benzodithiophene with alkylthienyl substituents displayed a higher performance due to their enhanced solubility and stronger donating ability of the donor unit.;Chapter 4 focuses on the effects of surface treatment of field-effect transistors with various organic silanes on the field-effect mobility of two benzodithiophene semiconducting polymers. Water contact angle measurements were used to correlate the change in hydrophobicity of the surface with field-effect mobility of the investigated polymers.