Abstract
The planar benzotrithiophene unit (BTT) was incorporated into four different donor polymers, and by systematically changing the nature and positioning of the solubilizing alkyl side chains along the conjugated backbone, the polymers’ frontier energy levels and optoelectronic properties were controlled. Reducing the steric hindrance along the polymer backbone lead to strong interchain aggregation and highly ordered thin films, achieving hole mobilities of 0.04 cm2/(V s) in organic thin film transistors. In an attempt to increase the polymer’s processability and reduce chain aggregation, steric hindrance between alkyl side chains was exploited. As a result of the increased solubility, the film forming properties of the polymer could be improved, but at the cost of reduced hole mobilities in OFET devices, due to the lack of long-range order in the polymer films.
Highlights
Silicon is one of the most common semiconductors used in the fabrication of electronic components, despite the high production costs of electronic grade silicon and its very brittle character
Based donor copolymers (Scheme 1), on which electronwithdrawing carbonyl groups have been introduced to the polymer backbone to modulate the polymer’s frontier energy levels, allowing us to investigate the effects on charge carrier mobilities and device lifetimes
A significant portion of the lowest unoccupied molecular orbital (LUMO) is located on the carbonyl group of the COBTT unit, whereas in the case of the BTT moiety, the LUMO is mainly located on the BTT core and not on the attached alkyl chain
Summary
Silicon is one of the most common semiconductors used in the fabrication of electronic components, despite the high production costs of electronic grade silicon and its very brittle character. Cheaper and more versatile semiconductors based on organic materials are poised to enter the market, especially for applications requiring flexible substrates and low manufacturing costs (i.e., thin flexible displays, one-way electronics, radiofrequency identification tags, etc.).[1] to gain market share over inorganic silicon, it will not be enough for organic semiconductors to be compatible with flexible substrates and cheaper in production than silicon, but they will have to achieve comparable electronic properties, notably similar carrier mobilities (∼1 cm2/(V s) for amorphous silicon) and lifetimes. Extensive work has been done in recent years to investigate how the molecular structure of semiconducting polymers influences the charge carrier mobility and what parameters can be modified to enhance device lifetime and processability.[2−9]. Based donor copolymers (Scheme 1), on which electronwithdrawing carbonyl groups have been introduced to the polymer backbone to modulate the polymer’s frontier energy levels, allowing us to investigate the effects on charge carrier mobilities and device lifetimes. The carbonyl groups influence the electronic structure of the materials and have a significant influence on the molecular packing and the solubility of the polymers; a second set of polymers with head-to-head alkyl chain arrangement was synthesized to increase solubility in organic solvents
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