particularly in terms of rectification ratio (R), has been improved considerably by introducing molecular dipoles, [3] asymmetric molecule-electrode interface, [4] donor-acceptor (D-A) dyads [5] or asymmetrically positioned redox-compounds. [6] However, the threshold voltage (defined as the voltage at which the current increases sharply in the direction of forward bias) of a diode, which is as important as R, has been rarely explored. This can be attributed to the fact that the designed energetic structure of a molecular junction is mismatched in reality due to strong Fermilevel pinning of the molecular frontier orbitals. [7] This can also be attributed to the fact that the chemical modifications of molecules cause undesired changes in the supramolecular structure of the junctions. [8] We report a new series of molecular diodes based on self-assembled monolayers (SAMs) composed of π-extended tetrathiafulvalene (exTTF). The effective threshold voltage of the diodes can be tuned to >1.0 V by introducing electron-withdrawing or electron-donating groups such as chlorine atoms or amino groups. These substitutional groups can efficiently generate an energy difference of the maximum magnitude of 0.6 eV for the highest occupied molecular orbital (HOMO) located on exTTF. This molecular design was accompanied by minimum changes in the supramolecular structure of the junctions. The control over the tunable threshold voltage at the molecular level can help in designing molecular functional devices in the future.It has been widely reported that it is difficult to control the process of charge transport in molecular junctions to overcome strong Fermi-level pinning. Bergren and McCreery et al. reported that tunneling barriers from aliphatic and aromatic molecules were compressed so that they were close to the Fermi level of the bottom electrode. [9] Frisbie et al. found that the desired energy-level alignment could not be achieved by replacing metal electrodes. [10] A few researchers have reported that the energy-level alignment can be tuned. For example, Veciana and Nijhuis et al. switched the polychlorotriphenylmethyl units, which provide molecular frontier orbitals, between the radical and nonradical form via a chemical modification to modulate the tunneling rate [11] or rectification ratio. [5a] Monti et al. demonstrated that small chemical substituents could be used to shift HOMO to regulate the energy-level alignment.It is a challenge to control the threshold voltage (defined as the voltage at which the current density increases sharply in the direction of forward bias), one of the basic parameters that define a molecular diode. The problem is that strong Fermi-level pinning of molecular frontier orbitals and the changes in the electronic structure are often overshadowed by the changes in the supramolecular structure. A chemical control approach is proposed to shift the effective threshold voltage of a series of molecular diodes composed of self-assembled monolayers (SAMs) of π-extended tetrathiafulvalene (exTTF) der...

Singlet exciton fission (SF) is believed to have the potential to break the Shockley−Quiesser third-generation solar cell devices, so that attracted great attention. Conventional linear acene based SF materials generally...

The study of tunneling through proteins is essential for the understanding of complicated electrochemical processes in biological activities. Both electron transport and transfer phenomena are found in protein junctions, but the reason remains unknown. In this work, we polymerized an ionic liquid into a conductive and exible electrode, and used it as a top-contact to form highly reproducible molecular junctions of protein molecules on a silver bottom-electrode. The junctions of proteins, choice of which including human serum albumin, cytochrome C or hemoglobin, show temperature independent electron transport characteristics, when junctions are in solid states; but all junctions can be switched to temperature dependent electron transfer, when junctions are hydrated in water. We experimentally for the rst time show that it requires about 100 − 120 meV for electrons passing through one heme group inside a hydrated protein molecule.

Charge Transport In article number 2300663, Yuan Li and co‐workers report a switch of the tunneling mechanism in protein junctions by change of the environmental conditions, which is achieved by the measurement of ionogel–protein–silver tunnel junctions in either the solid state or water. The person walking straight through the desert represents electron tunneling in the solid state, while the other person jumping above a river represents electron hopping in water.

Simplified and energy-efficient electronic devices that respond to multiple external stimuli (e.g., voltage, light, and mechanical stress) are needed for nascent technologies ranging from soft robotics and neuromorphic computing to Internet-of-Things1-3. Yet most research to-date focused on one switching modality with one stimulus4-6. Here we align materials design with device technology by introducing mechanical control over photoswitching leading to a new type of dual-gated molecular switch. While molecular switches are inherently energy-efficient7, theoretically ultrafast molecular photoswitches showed disappointing performance to-date, with small on/off ratio of electric current, poor reproducibility, and slow or stochastic switching8,9. It has been particularly challenging to develop efficient photoswitches in molecular tunnel junctions due to quenching and spontaneous back-switching10. On the other hand, molecular mechanical switches have been seldom reported11, despite wide implementation of mechanically-controlled switches12-14. Here, we use mechanical bending of the supporting electrode to direct molecular self-assembly of aggregation-induced emission (AIE) active molecules15,16, which allows us modulate the current under both light and mechanical force. This results in rapid, strong, reliable and sustained molecular switching. The high-performance photoswitch is 10-100 times faster than other approaches with on/off ratio of (3.8±0.1)×103 during 1600 bright/dark cycles under mechanical force, providing an alternative design route for flexible electronics and optomechatronics.