oa Comparative Assessment of Conjugated Polymers for High Performance Plastic Electronics

Conjugated polymers (CPs) are emerging active materials for electronic and optoelectronic devices, such as organic solar cells, thin-film transistors, light-emitting diodes, as well as optical and amperometric sensors. There has been an intensive worldwide research effort on the development of stable, organic semiconductors as potential replacements for amorphous silicon, the benchmark large area, amorphous semiconductor. ID TechEx, the UK-based market research company, “estimates that over the last two decades global investments into plastic electronics technologies exceed US $10 billion, and predict that this will grow to almost US $25 billion by 2020”.1 The ecological and commercial motivation to implement the use of plastic electronics is compelling. Recently, such efforts have facilitated the development of thin film transistors for backplane applications such as e-paper. The ability to operate in ambient atmosphere without costly and rigorous encapsulation barriers to avoid water and/or oxygen is an important step towards commercialization. Despite ever increasing numbers of newly developed conjugated polymers, the performance of CP thin films in optoelectronic devices prepared by the current fabrication methods has been rather limited largely due to the disordered structure. Liquid crystalline polymers (LCPs) have been widely investigated for various optical, mechanical, and electrical applications due to their unique ordered nature. In general LCP design, rod-like mesogens having a large aspect ratio are connected through somewhat flexible linker units to form a main-chain or as a side chain LCP to a flexible polymer. This design allows good molecular interactions between mesogens, but prevents regularly structured crystal formation. Therefore, it is highly desired to devise a novel and universal molecular design strategy to achieve lyotropic liquid crystalline CPs that can be easily processed to form a macroscopically assembled and aligned structure. The synthesis of well-defined conjugated molecules/polymers is a considerable synthetic challenge that many excellent research groups have addressed over the last decade or so. A particularly promising class of potential donor/acceptor materials for use in organic electronics for solution processed polymers is the promising Indacenodithiophene (IDT) unit. Herein we will report our synthetic efforts in the development of innovative polymeric materials containing a suit of wisely selected side chains and having different bridging atoms by replacing IDT with indacenodithiozole (IDDT) system. When incorporated into small molecules or polymers, this structure affords very narrow band-gaps capable of harvesting a large percentage of the solar flux. References; (1) http://ukplaticelectronics.com, C. G.-U. P. E.