Inverse Rectification in Donor–Acceptor Molecular Heterojunctions

Abstract

The transport properties of a junction consisting of small donor-acceptor molecules bound to Au electrodes are studied and understood in terms of its hybrid donor-acceptor-electrode interfaces. A newly synthesized donor-acceptor molecule consisting of a bithiophene donor and a naphthalenediimide acceptor separated by a conjugated phenylacetylene bridge and a nonconjugated end group shows rectification in the reverse polarization, behavior opposite to that observed in mesoscopic p-n junctions. Solution-based spectroscopic measurements demonstrate that the molecule retains many of its original constituent properties, suggesting a weak hybridization between the wave functions of the donor and acceptor moieties, even in the presence of a conjugated bridge. Differential conductance measurements for biases as high as 1.5 V are reported and indicate a large asymmetry in the orbital contributions to transport arising from disproportionate electronic coupling at anode-donor and acceptor-cathode interfaces. A semi-empirical single Lorentzian coherent transport model, developed from experimental data and density functional theory based calculations, is found to explain the inverse rectification.

A Molecular Diode with a Statistically Robust Rectification Ratio of Three Orders of Magnitude

“…Indeed, most molecular diodes based on, for instance, asymmetric molecule−electrode contacts, 14−16 embedded dipoles (or push−pull molecules), 17 donor−bridge−acceptor moieties (following the original design by Ratner and Aviram 18 ), or one asymmetrically positioned donor or acceptor group inside the junction, 19−21 yielded so far rectification ratios R = |J(V for )/J(V rev )| < 10 (V for = forward bias; V rev = reverse bias; J = current density in A/cm 2 ). 22 −25 Stadler et al 23 showed theoretically that molecular diodes in the coherent tunneling regime likely cannot achieve values of R > 20.…”

Measurement and understanding of single-molecule break junction rectification caused by asymmetric contacts

“…The experimental attempts of a single-molecule rectifier will pave steps towards future functional molecular electronic devices. Since first proposed by Aviram and Ratner, 1 molecular rectifier has gained considerable attention in both experimental designs [2][3][4][5] and theoretical simulations. 6,7 One of the most promising candidates stems from a molecular heterojunction which describes a molecular junction with asymmetric conformation.…”

Magneto-electronics properties of fluorine-passivated “Christmas Tree” graphene nanoribbons

“…The geometric optimization as well as calculations of the electronic structure and transport are performed by using the spin-polarized DFT combined with the non-equilibrium Green's function (NEGF) method [12], which has been confirmed that they are able to give results agreeing quantitatively well with experiments [13][14][15]. We employ Troullier-Martins norm-conserving pseudopotentials to represent the atom core and linear combinations of local atomic orbitals to expand the valence states of electrons.…”