Synthesis, characterization and application of n-dithieno[3,2-B:2’,3’-D]pyrroles/fluorene derivatives based conjugated molecules/polymers

• Main Author: Lu, Yong
• Other Authors: Ng Siu Choon
• Format: Theses and Dissertations
• Language: English
• Published: 2012
• Subjects: DRNTU::Engineering::Chemical engineering::Polymers and polymer manufacture
• Online Access: https://hdl.handle.net/10356/47586
• Institution: Nanyang Technological University

Semiconducting conjugated materials have attracted intensive interests during recent decades due to their potential applicability in organic electronics, such as organic photovoltaics and organic transistors. The structural modification of conjugated materials significantly influences their optical and electronic properties. This dissertation examined novel conjugated materials based on N-functionalized dithieno[3,2-b:2’,3’-d]pyrrole (DTP) and fluorene derivatives. The study was focused on the preparation and characterization of donor and acceptor (p- and n-type) materials which are potential candidates in organic electronics. For the p-type materials, polymers based on N-functionalized DTP units have been prepared using Stille coupling reactions with good yields in Chapter 3 and 4. Their structures are confirmed by NMR and elemental analyses. They are soluble in common organic solvents such as chloroform and THF. TGA results showed that they have good thermal stability. The investigation of their optical and electrical properties revealed that these polymers (discussed in chapter 3 and chapter 4) are low band gap (<1.8 eV) polymers. Polymers with such low band gaps are beneficial for light harvesting and are promising donor materials for organic solar cells. Consequently, organic photovoltaic devices based on the blend of selected polymers (donor) and PCBM (acceptor) are fabricated and investigated and preliminary results show that a PCE of 0.51% can be achieved based on polymer containing DTP moiety as donor material. In addition, in order to investigate side chain influence on polymer’s properties, in Chapter 5, a series of DTP and fluorene copolymers were prepared. The polymers physical, optical and electrical properties are characterized and discussed. The results indicate that the side chain of the polymer can influence the polymer’s solubility as well as their optical and electrical properties. It is generally believed that the rigid and planar structures of these polymers can facilitate charge transfer. Accordingly, these polymers are potential candidates in the application of organic electronics such as OFETs. For the n-type materials, novel bisfluorenyl substituted perylene diimide (Chapter 6) has been prepared and investigated. Its structure characterized by NMR and MS analysis. The oligomer is soluble in common organic solvents such as chloroform, THF and toluene. TGA results show that it has good thermal stability, whilst the electrical results indicate that the oligomer is a comparable accepter material to PCBM. Organic photovoltaic devices based on the blend of P3HT (donor) and the oligomer (acceptor) are fabricated and their device characteristic investigated. So far power conversation efficiency of 0.13% can be achieved based on the device. In addition, polymers based on tetrabenzo[5,5] and fluorone (Chapter 7 and Chapter 8) have been synthesized and their structures characterized. These polymers are soluble in common organic solvents and thermally stable. Investigations on the electrical properties of these polymers shows that they all have electron accepting characteristics, and thus are potential candidates for acceptor materials in organic electronics.