Tuning of Optical and Charge Transport Properties in Linear and Star-shaped Thiophene Based Organic Materials: A DFT Insight

Abstract

Organic materials are fascinating class of materials for large-area and flexible devices for organic semiconductors. Among them thiophene based organic semiconductors with new molecular and macromolecularstructures were explored for the possible applications in optoelectronic devices. The present thesis is divided into five chapters. Chapter 1 includes introduction of organic materials, and their optical, electronic and charge transport properties in these materials are studied in this chapter. Literature survey on thiophene based organic materials and methodology used in achieving the goal are also discussed in this chapter. In Chapter 2, the study starts with simple thiophene based linear acene molecules and calculation of their charge transport parameters using DFT methodology. Further to make study broader and comparative, furan and selenophene based acene molecules are also included. Chapter 3 divided into two subchapters, first part of the chapter deals with optical and charge transport properties of benzotrithiophene (BTT) and their possible isomers. It is shown that the studied isomers are better for hole and electron transport materials. The second part of the chapter 3 deals with the study of optical and transport properties of oligomers of BTT (most stable isomer). It is shown that the addition of BTT-units to the core BTT, results in enhanced charge transport properties. Chapter 4 also discussed in two parts, first part of chapter 4 deals with the study of linear optical and charge transport properties of heteroatomic (O, NH and Se) analogues of BTT isomers. In the second part of chapter 4 is on the study of truxene & isotruxene, thiatruxene & isothiatruxene and their heteroatomic (N, O and Si) analogue and shown that thiatruxene are better for hole transporting material while azatruxene are better for electron transporting materials. Last chapter (i.e. chapter 5) deals with impact of replacement of central benzene ring in anthracene with different heterocyclic ring on optical and charge transport properties in anthratetrathiophene (ATT) and anthratetrathiazole (ATTz) molecules. It is also studied the effect of heteroatom (S and N) on charge transport parameters at the periphery on ATTz molecule. Overall, aim of the thesis is to design those organic materials which are having high hole and electron transport properties and may find applications in organic semiconductor materials.