Organic metal electrodes

Takahashi Y, Hasegawa T, Abe Y, Tokura T, Saito G (2006) Organic metal electrodes for controlled p- and n-type carrier injections in organic field-effect transistors. Appl Phys Lett... 

FIGURE 2.1. Two possible carrier injection mechanisms at the organic/metal electrode interface (a) Schottky-type carrier injection via impurity or structural disordered levels with thermal assistance and (b) Fowler-Nordheim tunneling carrier injection with the assistance of a local high electric field (106—107 V/cm). 

In a similar manner, but with no necessity to add an electron acceptor, an assay of cholesterol has been designed using an organic metal electrode of NMP+TCNQ (Wollenberger, 1984). HRP was adsorbed on this material and covered by nylon-bound COD. The electrode was polarized at +25 mV to obtain a signal upon addition of cholesterol. The working stability of this sensor was poor. 

The metallic electrode materials are characterized by their Fermi levels. The position of the Fermi level relative to the eneigetic levels of the organic layer determines the potential barrier for charge carrier injection. The workfunction of most metal electrodes relative to vacuum are tabulated [103]. However, this nominal value will usually strongly differ from the effective workfunction in the device due to interactions of the metallic- with the organic material, which can be of physical or chemical nature [104-106]. Therefore, to calculate the potential barrier height at the interface, the effective work function of the metal and the effective ionization potential and electron affinity of the organic material at the interface have to be measured [55, 107],... 

There have been numerous studies of the electrical and emission properties of conjugated polymer-, small molecule-, and molecularly doped polymer-based OLEDs. The current-voltage and radiance-voltage characteristics have been nica sured as a function of thickness of the organic layer, temperature, different metal electrodes, etc. in an attempt to understand the device physics. A major factor in hibiting progress is the purity of the organic impurities that are incorporated dur-... 

The simplest and most widely used model to explain the response of organic photovoltaic devices under illumination is a metal-insulaior-metal (MIM) tunnel diode [55] with asymmetrical work-function metal electrodes (see Fig. 15-10). In forward bias, holes from the high work-function metal and electrons from the low work-function metal are injected into the organic semiconductor thin film. Because of the asymmetry of the work-functions for the two different metals, forward bias currents are orders of magnitude larger than reverse bias currents at low voltages. The expansion of the current transport model described above to a carrier generation term was not taken into account until now. 

Figure 13-4. Encigy level diagnim of a single-layer OLED, where the organic malerial is depicted as a fully depleted semiconductor. The valence band Ey corresponds to the HOMO and the conduction band Ec corresponds to the LUMO. Tile Fermi levels of the two metal electrodes are marked as Et-. Upon contact a built-in potential is established and needs to be compensated for, before the device will begin to operating.

Beden, B. Electrocatalytic Oxidation of Oxygenated Aliphatic Organic Compounds at Noble Metal Electrodes 22... 

Breiter, M. W. Adsorption of Organic Species on Platinum Metal Electrodes 10... 

Beden, C. Lamy, and J.-M. Leger, Electrocatalytic Oxidation of Oxygenated Aliphatic Organic Compounds at Noble Metal Electrodes, in Modem Aspects of Electrochemistry, Vol. 22, Ed. by J. O M. Bockris, B. E. Conway, and R. E. White, Plenum Press, New York, 1992, pp. 97-264. 

Aliphatic Organic Compounds at Noble Metal Electrodes... 

For the cathodic reduction of organic substances, electrodes of two types are used the platinum and the mercury type. Those of the first type (platinum metals, and in alkaline solutions nickel) exfiibit low polarization in hydrogen evolution their potential can be pushed in the negative direction no further than to -0.3 V (RHE). Hydrogen readily adsorbs on these electrodes, which is favorable for reduction... 

Pleith, W., W. Kozlowski, and T. Twomey, Reflectance spectroscopy and ellipsometry of organic monolayers, in Adsorption of Molecules at Metal Electrodes, 3. Lipkowski and P. N. Ross, Eds., VCH, New York, 1992, p. 285. 

Appreciable interest was stirred by the sucessful use of nonmetallic catalysts such as oxides and organic metal complexes in electrochemical reactions. From 1968 on, work on the development of electrocatalysts on the basis of the mixed oxides of titanium and ruthenium led to the fabrication of active, low-wear electrodes for anodic chlorine evolution which under the designation dimensionally stable anodes (DSA) became a workhorse of the chlorine industry. 

Accidental surface impurities can have most diverse origins. On the surfaces of smooth metal electrodes obtained by metallurgical methods, one almost always finds carbon species produced by thermal destruction of organic material that had somehow arrived on the surface. Often, impurities arrive on an electrode surface when it comes into contact with an insufficiently purified electrolyte. 

Simple Oxides of Base Metals Electrodes of lead dioxide, Pb02, which in contrast to other base-metal oxides are stable in sulfuric acid are an example for a simple oxide system. In a number of cases, this electrode serves as the anode in the electrosynthesis of organic compounds in acid media. 

On detailed electrical characteristics of a SET transistor utilizing charging effects on metal nanoclusters were reported by Sato et al. [26]. A self-assembled chain of colloidal gold nanoparticles was connected to metal electrodes, which were formed by electron-beam lithography. The cross-linking of the particles as well as their connection to the electrodes results from a linkage by bifunctional organic molecules, which present the tunnel barriers. 

Mechanisms of the Oxidation of Carbon Monoxide and Small Organic Molecules at Metal Electrodes... 

Beden B, Lamy C, Leger JM. 1992. Electrocatalytic oxidation of oxygenated aliphatic organic compounds at noble metal electrodes. In Bockris JO M, Conway BE, White RE, eds. Modem Aspects of Electrochemistry. Volume 22. New York Plenum Press, p 97-264. 

The previous analysis indicates that although the voltammetiic behavior suggests that the aqueous phase behaves as a metal electrode dipped into the organic phase, the interfacial concentration of the aqueous redox couple does exhibit a dependence on the Galvani potential difference. In this sense, it is not necessary to invoke potential perturbations due to interfacial ion pairing in order to account for deviations from the Butler Volmer behavior [63]. This phenomenon has also been discarded in recent studies of the same system based on SECM [46]. In this work, the authors observed a potential independent ket for the reaction sequence. 

---