Electroconductive π-Junction Au Nanoparticles

Abstract

The fabrication of printed electronic circuits using solution-based electroconductive materials at low temperature is essential for the realization of modern printed electronics including transistors, photovoltaic cells, and light-emitting devices. Despite the progress in the field of semiconductor solution materials, reliable electrodes are always fabricated by a vacuum deposition process resulting in only partially solution-processed devices. In this paper, we show that planar phthalocyanine-conjugated Au nanoparticles (NPs) significantly improve the interparticle-carrier-transport properties. The deposition of a solution of the Au NPs under ambient conditions results in an electroconductive metallic thin film without further post-treatment. Maximum conductivity reaches >6600 S cm ¹1 and the conductivity remains unchanged for at least 1 year under ambient conditions. The all-solution-processed organic field-effect transistor (OFET) fabricated under ambient conditions exhibits mobility values as high as 2 cm 2 V ¹1 s ¹1, the value of which is comparable to OFET devices having vacuum-deposited Au electrodes.Electrodes are necessary in all types of electric devices such as transistors, photovoltaic cells, and light-emitting devices. These devices are commonly fabricated by employing expensive vacuum deposition processes. A promising alternative that is cheaper and faster for fabricating devices is wet printing using material from specially designed solutions.1 Many examples of solution processes for transistors, 210 photovoltaic cells, 11 and light-emitting devices 12 have been reported. However, in order to achieve high efficiency and reliable devices, vacuum-processed metals and conductive metal oxide electrodes must be used, thereby producing only partially solution-processed devices. To realize the fabrication of allsolution-processed devices, electrodes must be fabricated at relatively low temperatures from a solution, and the resultant electrode must fulfill three requirements: they must have (1) good contacts, i.e., low resistance at the semiconductor electrode interface, (2) high electroconductivity, and (3) high oxidation stability. In this study, we report that the Au nanoparticles (NPs) possessing orbital hybridization between the Au core and relatively large aromatic molecules meet these three requirements, and consequently, produce reliable electrodes that are comparable to vacuum-deposited Au electrodes.For the fabrication of NP-based electrodes under ambient conditions, surface ligands of inorganic NPs must meet two requirements: they must (1) adhere firmly to the NP surface for colloidal stabilization and (2) provide stable and facile carrier transport between NPs. We found that orbital hybridization between ³ orbitals of aromatic molecules and inorganic orbitals of the Au NPs improves the interparticle-carrier transport. The molecular orbital structure of aromatic compounds is altered when the ³-conjugated plane of aromatic compounds closely bonds while parallel to the metal surface, 1315 and thi...

Gold nanorods with conjugated polymer ligands: sintering-free conductive inks for printed electronics

“…Kanehara and coworkers synthesized tailored phthalocyanine ligands and demonstrated that aromatic systems can provide mobile electrons in the ligand shells. 2 , 12 We adapted this idea with polymer-coated particles and created hybrid particles with increased colloidal stability using commercially available conjugated polymers such as poly[2-(3-thienyl)-ethyloxy-4-butylsulfonate] (PTEBS) with an average molecular weight of 40–70 kDa. To ensure that the π-electrons couple to the metal surface, polythiophene derivatives were used; they bring the π-system in close proximity to the gold because they contain a sulfur heteroatom in the aromatic ring.…”

Ligand effect on the catalytic activity of porphyrin-protected gold clusters in the electrochemical hydrogen evolution reaction

“…Therefore, we concluded that the obtained AuCs were protected by SC n P in a face-coordinated fashion, as previously reported. 6 , 9 SC n P/AuNPs of 2.2 or 3.8 nm in size were synthesized by the reduction of Au precursor at –50 or 0 °C, respectively ( Fig. 2b, c, e, and f ).…”

The role of ligands in coinage-metal nanoparticles for electronics

“…Ligand exchange may be necessary after synthesis to enable formulations with solvents that are suitable for deposition [ 83 ]. It is also possible to replace insulating ligands from synthesis with conductive moieties in order to avoid later sintering steps [ 83 – 84 ].…”