2 research outputs found
Synthesis of Perylene Imide Diones as Platforms for the Development of Pyrazine Based Organic Semiconductors
There is a great
interest in peryleneimide (PI)-containing compounds
given their unique combination of good electron accepting ability,
high abosorption in the visible region, and outstanding chemical,
thermal, and photochemical stabilities. Thus, herein we report the
synthesis of perylene imide derivatives endowed with a 1,2-diketone
functionality (<b>PIDs</b>) as efficient intermediates to easily
access peryleneimide (PI)-containing organic semiconductors with enhanced
absorption cross-section for the design of tunable semiconductor organic
materials. Three processable organic molecular semiconductors containing
thiophene and terthiophene moieties, <b>PITa</b>, <b>PITb</b>, and <b>PITT</b>, have been prepared from the novel <b>PIDs</b>. The tendency of these semiconductors for molecular aggregation
have been investigated by NMR spectroscopy and supported by quantum
chemical calculations. 2D NMR experiments and theoretical calculations
point to an antiparallel π-stacking interaction as the most
stable conformation in the aggregates. Investigation of the optical
and electrochemical properties of the materials is also reported and
analyzed in combination with DFT calculations. Although the derivatives
presented here show modest electron mobilities of ∼10<sup>–4</sup> cm<sup>2</sup>V<sup>–1</sup>s<sup>–1</sup>, these
preliminary studies of their performance in organic field effect transistors
(OFETs) indicate the potential of these new building blocks as n-type
semiconductors
Mobility versus Alignment of a Semiconducting π‑Extended Discotic Liquid-Crystalline Triindole
The
p-type semiconducting properties of a triphenylene-fused triindole
mesogen, have been studied by applying two complementary methods which
have different alignment requirements. The attachment of only three
flexible alkyl chains to the nitrogen atoms of this π-extended
core is sufficient to induce columnar mesomorphism. High hole mobility
values (0.65 cm<sup>2</sup> V<sup>–1</sup> s<sup>–1</sup>) have been estimated by space-charge limited current (SCLC) measurements
in a diode-like structure which are easily prepared from the melt,
rendering this material a good candidate for OPVs and OLEDs devices.
The mobility predicted theoretically via a hole-hopping mechanism
is in very good agreement with the experimental values determined
at the SCLC regime. On the other hand the hole mobility determined
on solution processed thin film transistors (OFETs) is significantly
lower, which can be rationalized by the high tendency of these large
molecules to align on surfaces with their extended π-conjugated
core parallel to the substrate as demonstrated by SERS. Despite the
differences obtained with the two methods, the acceptable performance
found on OFETs fabricated by simple drop-casting processing of such
an enlarged aromatic core is remarkable and suggests facile hopping
between neighboring molecular columns owing to the large conducting/isolating
ratio found in this discotic compound