  Solution-processed organic semiconductors enable the fabrication of
large-area and flexible electronics by means of cost-effective, solution-based
mass manufacturing techniques. However, for many applications an insoluble
active layer can offer technological advantages in terms of robustness to
processing solvents. This is particularly relevant in field-effect transistors
(FET), where processing of dielectrics or barriers from solution on top of the
semiconductor layer typically imposes the use of orthogonal solvents in order
not to interfere with the nanometer thick accumulation channel. To this end,
the use of latent pigments, highly soluble molecules which can produce
insoluble films after a post-deposition thermal cleavage of solubilizing
groups, is a very promising strategy. In this contribution, we demonstrate the
use of tert-Butyloxycarbonyl (t-Boc) functionalized diketopyrrolopyrrole and
perylene-diimide small molecules for good hole and electron transporting films.
t-Boc thermal cleavage produces a densification of the films, along with a
strong structural rearrangement of the deprotected molecules, strongly
improving charge mobility in both p- and n-type FET. We also highlight the
robustness of these highly insoluble semiconducting layers to typical and
aggressive processing solvents. These results can greatly enhance the degree of
freedom in the manufacturing of multi-layered organic electronic devices,
offering enhanced stability to harsh processing steps.
