The
planar benzotrithiophene unit (<b>BTT</b>) 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 cm<sup>2</sup>/(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
