Synthese von Indacenodithiophen-basierten Copolymeren mittels direkter C-H-Arylierungspolykondensation

Organic semiconducting polymers are widely employed in organic electronics such as organic photovoltaics (OPVs), organic field-effect transistors (OFETs) and organic light emitting diodes (OLEDs). Their remarkable mechanical and charge transport properties as well as solution processability allow low-cost fabrication of light-weight and flexible devices. Among them indacenodithiophene (IDT)-based materials are promising candidates for application in organic electronics. Due to their low energetic disorder, extended conjugation and high electron density the IDT-based polymers show high field-effect mobilities and high absorption coefficients. However, their synthesis suffers from long reaction sequences and is often accomplished using toxic materials. Commercialization requires development of more efficient and sustainable reaction pathways to ease tailoring of structures and to limit molecular defects. Herein, the development of new synthetic pathways towards IDT-based polymers is presented in which all C-C coupling steps are achieved by C-H activation – an atom-economic alternative to conventional transition-metal catalyzed cross couplings. Two different strategies were established to synthesize a series of well-defined IDT-based homo- and copolymers with different side chain patterns and varied molecular weights. The first way starts by synthesis of a precursor polymer and subsequent cyclization affording IDT homopolymers. In the second approach, cyclized IDT monomers were prepared first and then polymerized using direct arylation polycondensation (DAP) yielding IDT homo- and copolymers. The synthetic pathways were optimized in terms of maximizing molecular weights and limiting defect structures. While the first pathway enables synthesis of well-defined homopolymers, the latter is the method of choice for preparation of IDT-based copolymers in high yields and adjustable molecular weights. The polymers were further characterized in detail by optical, thermal, electrical and morphological analyses. OFETs as well as all-polymer solar cells (all-PSCs) were fabricated to investigate the influence of structural modifications and molecular weight on their optoelectronic performance. Thus, this thesis provides a comprehensive study of the structure-property correlations of IDT-based polymers and simplified synthetic protocols for the design and preparation of donor-acceptor copolymers in the future