Transport Properties of a Single-Molecule Diode

Abstract

Charge transport through single diblock dipyrimidinyl diphenyl molecules consisting of a donor and acceptor moiety was measured in the low-bias regime and as a function of bias at different temperatures using the mechanically controllable break-junction technique. Conductance histograms acquired at 10 mV reveal two distinct peaks, separated by a factor of 1.5, representing the two orientations of the single molecule with respect to the applied bias. The current-voltage characteristics exhibit a temperature-independent rectification of up to a factor of 10 in the temperature range between 300 and 50 K with single-molecule currents of 45-70 nA at ±1.5 V. The current-voltage characteristics are discussed using a semiempirical model assuming a variable coupling of the molecular energy levels as well as a nonsymmetric voltage drop across the molecular junction, thus shifting the energy levels accordingly. The excellent agreement of the data with the proposed model suggests that the rectification originates from an asymmetric Coulomb blockade in combination with an electric-field-induced level shifting.

Controlling the direction of rectification in a molecular diode

“…Coupling the molecular frontier orbital to one electrode (or both) is key to generate electronic function with optimal device performance for a range of applications including molecular-based rectification, spin-transport and memory [8][9][10][11][12] . Strong electronic coupling ensures that the molecular frontier orbital efficiently follows the Fermi level of the electrode to which it is coupled under bias, but it results in hybridization of orbitals and in a corresponding broadening of the molecular energy levels and large leakage currents 8 .…”

A Toolbox for Controlling the Energetics and Localization of Electronic States in Self‐Assembled Organic Monolayers

“…For the dipolar section substituted bypirimidine ( n = 2) has been chosen, as pyrimidine‐containing systems have large dipole moments,36 allow for large work‐function changes,31 can be well integrated into conjugated backbones, and have been successfully synthesized and studied experimentally as potential molecular rectifiers 41, 42, 43. For the most simple systems discussed in the following we use a structure inspired by SAMs studied already experimentally to show the feasibility of the suggested approach.…”

Disorder-Induced Rectification in a Molecular System

“…We assume the wideband limit [23], 5 where the real part can be neglected, and the matrix elements of the imaginary part are given by…”

“…In order to achieve this, a variety of manufacturing techniques has been developed in the past to those of previous works in the literature that found current rectification due to asymmetric bindings to the leads [5,16]. It is well known that asymmetric couplings of the central molecule to the electrodes result in an uneven distribution of the voltage drop between the contacts, which induces rectification.…”