Synthesis of Chalcogenophene Containing π-Conjugated Polymers for Field Effect Transistors

Bedi, Anjan (2014) Synthesis of Chalcogenophene Containing π-Conjugated Polymers for Field Effect Transistors. PhD thesis, Indian Institute of Science Education And Research Kolkata.

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Abstract

This thesis deals with the new chalcogenophene based -conjugated solution-processable copolymers and their applications in field effect transistors, photovoltaic devices and as polymer electrochromic materials. In the earlier part of the thesis, the novel copolymers comprising cyclopenta[c]thiophene (CPT) as donor and benzodiazole as acceptor have been synthesized and characterized by their PFET and PSC performances as well as tunability of the band gap with simple atomistic modification in the benzodiazole unit. The next part of the thesis deals with the coplanar polymers containing CPT and bithiazole (BTz). The combination of CPT and BTz units in the resulting polymers showed the higher crystalline nature thus, in turn, improvement in charge carrier mobility was observed to reach to the highest among any CPT containing polymer. Further, 5,5-bis(dodecyloxymethyl)-5,6-dihydro-4H-cyclopenta[c]selenophene was synthesized for the first time and reported with its crystal structure, which is the first report of any crystallographic characterization of cyclopenta[c]selenophene. This was utilized for preparing low band gap polymer by copolymerizing with vinylene units and compared with its thiophene analogue in terms of optoelectronic properties and transistor performances. In the later part of the thesis, the electroactivity of benzo[1,2-b:4,3-b']dithiophene (BdT) was explored via its thiophene and selenophene capped comonomers. Electrochemical stability and electrochromic switching ability of the electrochemically polymerized solution-processable polymers were probed. The switching of the emission color for the comonomers and the copolymers were also investigated. In the last part of the thesis, the formation of a BdT and BTz based chiral copolymer from two optically inactive reactants in absence of any internal or external chiral influence was investigated. The improvement in transistor performances and growth of localized crystalline nature of the polymers were also examined with thermal annealing.

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