Guidelines and diagnostics for charge carrier tuning in thiophene-based wires

Abstract

Reported experimental trends in charge carrier tuning in single molecule junctions of oligothiophene-based wires are rationalized by means of frontier molecular orbital theory. The length and substituent effects on the energy levels of the frontier orbitals have been shown to translate to the computed transmission spectra - with a caveat of the role of the linker group. The resulting transport (charge carrier) type - n- (electrons) or p- (holes) - is easily identifiable from the in silico charge transfer trends.

Hemilabile Ligands as Mechanosensitive Electrode Contacts for Molecular Electronics

“…Thepresence of multiple binding sites and the monodentateQbidentate contact transition was exploited to modulate the coupling parameter G as the junction is compressed and relaxed. Thej unctions displayed chemically controlled sensitivity,can operate at kHz speed and show no sign of fatigue for up to 1000 cycles.Inaddition to expanding the molecular-electronics toolbox with new design ideas for molecular termini and contacts,o ur results shed light on the mechanism of configuration transitions in thienyl-based hemilabile ligands,s howing that the fabrication of single-molecule junctions doubles also as avaluable characterisation tool to probe metal-ligand interactions.Furthermore,(methylthio)thiophenes and thiophenethiols are widely used as molecular-wire termini in molecular electronics, [36,39,[48][49][50][51][52][53][54] and our results unambiguously demonstrate that contact-configuration changes must be taken into account when interpreting their conductance-vs.-electrode-separation trajectories during asingle-entity break-junction experiment.…”

Conceptual Framework of Organic Electronics

“…We have addressed this challenge by analyzing the underlying factors defining the energy levels of the frontier MOs going from a single molecular building unit to the corresponding oligomer chain. [28] Importantly, we were able to detect the transport type crossover using a simple and inexpensive in silico diagnostic, namely the trend in the charge transfer between the molecular bridge and the electrode (Fig. 5A).…”

“…Chart shows changes in the partial charge on the thiophene dioxide oligomeric bridge in the junction with its increasing length, based on Hirshfeld population analysis. [28] (B) Computed zero-bias transmission values in linear acene, linear alkane, oligotwistane and designed carbon nanothread junctions, with representative structures shown on the right. [30] All computations are at PBE/DZP + ZORA level.…”

“…[39] Numerous studies have focused on the HLG engineering in these systems as means to enhance both their stability and conductivity, [40] establishing the trends and guidelines that we and others were able to extend to the molecular wire junctions. [27,28] Beyond the molecular structure, intermolecular (noncovalent) interactions also find parallel implications in semiconductors and dimer molecular junctions. In both types of assemblies, stronger electronic coupling V between the neighbor molecular units generally leads to better transport.…”

Charge transport and transfer phenomena involving conjugated acenes and heteroacenes

“…Although n-type organic semiconductors are rare, they are of complementary interest for the fabrication of p-n junctions as well as other logic circuits [51,67]. Stable n-type organic semiconductors have recently been realized by introducing electron withdrawing groups into thiophene-or acene-based oligomers which are intrinsically hole-transporting materials [68][69][70][71][72]. Such kind of carrier switching may also occur through stereo-electronic changes inside a molecule [73,74].…”