Diode anode

Electronic Vacuum Tube. In special electronic vacuum diode tubes, with spacing between the cathode and anode of 10 )J.m, high gas concentrations of some types are beneficial to the operation of the tube under proper control. 

In Fig. 15-9 two potentiostatically controlled protection rectifiers and an additional diode are included to drain peak currents. At pipeline crossings with an external rail network (e.g., in regions outside the urban area), the forced stray current drainage should be installed as close as possible to the rails that display negative potentials for the longest operation time. The currents absorbed from the positive rails continue to flow also in the region outside the rail crossings. Here the use of potentiostatically controlled rectifiers is recommended these should be connected not only to the rails but also to impressed current anodes. 

Pure aluminum is used in the electrolysis protection process, which does not passivate in the presence of chloride and sulfate ions. In water very low in salt with a conductivity of x < 40 yUS cm" the polarization can increase greatly, so that the necessary protection current density can no longer be reached. Further limits to its application exist at pH values < 6.0 and >8.5 because there the solubility of Al(OH)3 becomes too high and its film-forming action is lost [19]. The aluminum anodes are designed for a life of 2 to 3 years. After that they must be renewed. The protection currents are indicated by means of an ammeter and/or a current-operated light diode. In addition to the normal monitoring by service personnel, a qualified firm should inspect the rectifier equipment annually. 

Figure 13-13. (a) Currem-vollage data from MEH-PPV-bascd OLEDs willi Au anodes and various cathodes plotted according to E4. (13.5) (b) the external quantum efficiency for the diodes with Al and Ca cathodes The solid line represents the maximum efficiency of 2%. Reproduced with permission from 11511. Copy light 1998 by the American Physical Society. 

Figure 12-13 compares j(L ) characteristics for a single layer diode of polylluor-enone sandwiched between an ITO anode and either an aluminum or an magnesium cathode ]45]. The increase of the current upon replacing Al by Mg proves that in the latter case the majority of the earners must be electrons. At the same... 

Diode Dx is shown with its cathode connected to a positive voltage source +V. A diode cannot conduct unless the voltage across the anode is positive with respect to the cathode. As long as the voltage at the anode is less than that of the cathode, diode D does not conduct, and there is no output. At some point, anode voltage exceeds the bias value +V, and the diode conducts. The input signal is allowed to pass to the output. 

Y Cao, G Yu, C Zhang, R Menon, and AJ Heeger, Polymer light-emitting diodes with polyethylene dioxythiophene polystyrene sulfonate as the transparent anode, Synth. Met., 87 171-174, 1997. 

S.A. Carter, M. Angelopoulos, S. Karg, P.J. Brock, and J.C. Scott, Polymeric anodes for improved polymer light-emitting diode performance, Appl. Phys. Lett., 70 2067-2069, 1997. 

W.H. Kim, A.J. Makinen, N. Nikolov, R. Shashidhar, H. Kim, and Z.H. Kafafi, Molecular organic light-emitting diodes using highly conducting polymers as anodes, Appl. Phys. Lett., 80 3844-3846 (2002). 

L.S. Hung, L.R. Zheng, and M.G. Mason, Anode modification in organic light-emitting diodes by low-frequency plasma polymerization of CHF3, Appl. Phys. Lett., 78 673-675 (2001). 

J.S. Kim, M. Granstrom, R.H. Friend, N. Johansson, W.R. Salaneck, R. Daik, W.J. Feast, and F. Cacialli, Indium-tin oxide treatments for single- and double-layer polymeric light-emitting diodes the relation between the anode physical, chemical, and morphological properties and the device performance, J. Appl. Phys., 84 6859-6870, 1998. 

G.L. Frey, K.J. Reynolds, R.H. Friend, H. Cohen, and Y. Feldman, Solution-processed anodes from layer-structure materials for high efficiency polymer light-emitting diodes, Am. Chem. Soc., 125 5998-6007, 2003. 

K.J. Reynolds, G.L. Frey, and R.H. Friend, Solution-processed niobium diselenide as conductor and anode for polymer light-emitting diodes, Appl. Phys. Lett., 82 1123-1125, 2003. 

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