A unified
approach of directional solvent vapor annealing for crystal
alignment in solution-processed organic semiconductors is proposed.
Highly crystalline molecular self-assembly of the drop-cast technique
is further enhanced by postprocessing scheme of the solvent vapor annealing with additional benefit
of alignment of the crystalline domains. In this technique, a mixture
of carrier gas and solvent vapors are made to flow in a certain direction
and in the close proximity of the surface of the substrates carrying
the solution. Flow of the carrier gas imparts directionality to the
semiconducting crystalline ribbons, whereas the influx of the solvent
vapors improves the crystalline order in the semiconducting film.
The flow rate of the carrier gas and the position of the substrate
in the interaction chamber are the primary regulating factors, which
have the ability to provide a semiconducting layer with a well-aligned
and interconnected assembly of long ribbons. These favorable film
properties further materialize in the form of electrical performance
of the corresponding field-effect transistors. The versatility of
this technique makes it a viable alternative for the solution processing
of organic semiconductors.