3 research outputs found
Ab Initio Treatment of Disorder Effects in Amorphous Organic Materials: Toward Parameter Free Materials Simulation
Disordered organic materials have
a wide range of interesting applications,
such as organic light emitting diodes, organic photovoltaics, and
thin film electronics. To model electronic transport through such
materials it is essential to describe the energy distribution of the
available electronic states of the carriers in the material. Here,
we present a self-consistent, linear-scaling first-principles approach
to model environmental effects on the electronic properties of disordered
molecular systems. We apply our parameter free approach to calculate
the energy disorder distribution of localized charge states in a full
polaron model for two widely used benchmark-systems (trisÂ(8-hydroxyquinolinato)Âaluminum
(Alq<sub>3</sub>) and <i>N,N</i>′-bisÂ(1-naphthyl)-<i>N,N</i>′-diphenyl-1,1′-biphenyl-4,4′-diamine
(α-NPD)) and accurately reproduce the experimental charge carrier
mobility over a range of 4 orders of magnitude. The method can be
generalized to determine electronic and optical properties of more
complex systems, e.g. guest–host morphologies, organic–organic
interfaces, and thus offers the potential to significantly contribute
to de novo materials design
Spin-Crossover and Massive Anisotropy Switching of 5d Transition Metal Atoms on Graphene Nanoflakes
In spin crossover phenomena, the
magnetic moment of a molecule
is switched by external means. Here we theoretically predict that
several 5d-transition metals (TMs) adsorbed on finite graphene flakes
undergo a spin crossover, resulting from multiple adsorption minima,
that are absent in the zero-dimensional limit of benzene and the two-dimensional
limit of graphene. The different spin states are stable at finite
temperature and can be reversibly switched with an electric field.
The system undergoes a change in magnetic anisotropy upon spin crossover,
which facilitates read-out of the spin state. The TM-decorated nanoflakes
thus act as fully controlled single-ion magnetic switches
Highly Selective Dispersion of Single-Walled Carbon Nanotubes via Polymer Wrapping: A Combinatorial Study via Modular Conjugation
Fourteen
different “hairy-rod” conjugated polymers,
9,9-dioctylfluorene derivatives entailing 1,2,3-triazole, azomethine,
ethynyle, biphenyle, stilbene, and azobenzene lateral units, are synthesized
via modular conjugation and are systematically investigated with respect
to their ability to selectively disperse SWCNTs. Four polymers of
the azomethine type, with unprecedented selectivity toward dispersing
(8,7), (7,6), and (9,5) SWCNT species, have been identified. In particular,
azomethine polymers, herein applied for the first time for SWCNT dispersion,
have been evidenced to be very effective in the highly selective solubilization
of SWCNTs. The experimentally observed selectivity results are unambiguously
supported by molecular dynamics simulations that account for the geometrical
properties and deformation energy landscape of the polymer. Specifically,
the calculations accurately and with high precision predict the experimentally
observed selectivity for the (7,6) and (9,5) conformations