Electron excitation current density

As /a was found to increase with temperature [40,41], step (51) is believed to be an activated process, in which the electron must first be thermally excited from the Xj surface state to the conduction band edge before injection can occur. The corresponding current density is therefore usually referred to as the electron excitation current density. The reaction step with which reaction (51) is assumed to compete is then step (15) in the DH dissolution mechanism, step (37) in the DX mechanism, step (46) (or (46 )) in the DXC mechanism, and equally step (46) or (46 ) in the DHC mechanism, which we have hitherto not considered, and which comprises the following steps ... 

The number of integrated carriers, iV, is QA-Iwhere q is the electron charge. Because dark current, is a combination of thermal excitation processes, neglecting avalanche and tunneling, ideal performance occurs when the photon-induced current density Jp is greater than Fluctuations of N are the... 

The /3-diketonate [Nd(dbm)3bath] (see figs. 41 and 117) has a photoluminescence quantum efficiency of 0.33% in dmso-7r, solution at a 1 mM concentration. It has been introduced as the active 20-nm thick layer into an OLED having an ITO electrode with a sheet resistance of 40 il cm-2, TPD as hole transporting layer with a thickness of 40 nm, and bathocuproine (BCP) (40 nm) as the electron injection and transporting layer (see fig. 117). The electroluminescence spectrum is identical to the photoluminescence emission the luminescence intensity at 1.07 pm versus current density curve deviates from linearity from approximately 10 mA cm-2 on, due to triplet-triplet annihilation. Near-IR electroluminescent efficiency <2el has been determined by comparison with [Eu(dbm)3bath] for which the total photoluminescence quantum yield in dmso-tig at a concentration of 1 mM is Dpi, = 6% upon ligand excitation, while its external electroluminescence efficiency is 0.14% (3.2 cdm-2 at 1 mAcm-2) ... 

In a typical EEL spectrum, the count rate Ia (area under the excitation edge after background subtraction, for element A) is a product of the incident electron current density, J0, the number of atoms Na of element A per unit area, and oa> the total ionization cross-section per atom for the excitation of the appropriate inner-shell by the incident electrons. However, to preserve good energy resolution, an aperture is placed after the specimen which limits scattering to angles less than P and hence only a fraction of the core loss signal Ia(P) is measured. Moreover, in most... 

Koyama has examined the sensitization behavior of a series of pheophorbide sensitizers (112-117) with similar structure. The results indicate that the short-circuit current density as well as the overall solar energy-to-electricity conversion efficiency increased with the increasing Qy absorption and with the decreasing one electron-oxidation potential. Two empirical models are built based on the experimental results. One model suggests a parallel electron injection from both excited and ground states to the conduction band of Ti02 whereas the other one supports an electron injection via the excited state only, in which both the Qy absorption and the Qy-state one electron-oxidation potential can contribute [110]. 

Even more important for quantum energy converters, e.g., solar cells, than the energy current density is the photon current density, because it determines the rate at which electrons are excited. Neglecting impact ionisation effects, the excitation of one electron requires at least one absorbed photon. 

In order to derive Rosenfeld s equation from Eq. (3.14) we must make some such argument as the following. Let us assume that the self-consistent quantum field theory (Sect. 2) has been worked through and has yielded composite -particle elementary excitations that we identify with molecules. We can then define a charge and current density for a molecule containing n electrons and nuclei,... 

Although the reverse current of an ideal Schottky barrier is J, in practice there are other current soitfces. Imperfect contacts have a leakage current which generally increases exponentially with bias. Even with an ideal contact, there is a thermal generation current caused by the excitation of electrons and holes from bulk gap states to the band edges. This mechanism determines the Fermi energy position under deep depletion conditions. The current density is the product of the density of states and the excitation rate and is approximately. 

Thus in a uniform positive column discharge, the simultaneous occurrence of these two excitation processes by electron impact to an extent that would leave a considerable margin for energy absorption in other processes provides a mechanism that could account for the highest observed values given in Tables IV and V. But the crucial question is whether this mechanism can account for the trend of P/p and rj with X/p and with the current density j, and can also account for the absolute magnitudes observed. 

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