Electron trapping trap depth

Fading Loss of luminescence during storage. Anomalous fading refers to loss in excess of the thermal fading predicted from measurement of the relevant electron trap depth and frequency factor. 

Figure 9-19. Bund diagram of LPPP with hole traps and gold electrodes with Va<- vacuum level. Ec conduction band, Eva valence band. E, Fermi level. . baudgup energy. and , " trap depths. ,( ) trap distribution, X electron affmity, and All work function of the gold electrodes.

One can assume that the saturated residual potential, at the end of a large number of cycles, decays. As thermal release proceeds, holes are emitted and swept out from the specimen, resulting in a decrease in the measured surface potential. The decay rate of the saturated potential is strongly temperature dependent due to thermal release from deep mobility gap centers, located approximately 0.9 eV above for holes. The discharge of the saturated potential due to electron trapping occurs much more slowly. The reason is that the energy depth of electron traps from is about 1.2 eV, which is greater than that of hole traps from E. ... 

It is possible to assess the approximate depths of the electron and hole traps from spectral evolution data. This has been done in the case of WS2 nanoparticles from the analysis of the unpolarized component of the emission [68]. The emission following hole trapping (but prior to electron trapping) is only partially polarized and the emission following electron trapping is unpolarized. Thus, the unpolarized... 

If the electrons were simply trapped at the low temperature, the trap depth would have to be shallow enough to allow them to escape into the conduction band when the emulsion is warmed up hence, the trap depth would not exceed a few tenths of an electron volt. However, some electrons might combine with silver ions to form silver atoms even at the low temperature. When the emulsion is warmed up, these atoms either could dissociate... 

Mitchell (185) assigned to it the formula [irXg]- --2Ag, where Ag represents a silver ion vacancy. The complex acts as a transient electron trap. Eachus and Graves (191), from data obtained on Bridgman crystals, calculated a trap depth of 0.44 eV for the bromide complex in silver bromide. 

Sulfur sensitization increases both the depth of shallow electron traps and the stabilization energy of the silver-atom center. These changes are sufficient to account for the overall increase in sensitivity" and its subsequent decrease at concentrations above the optimum. The population of free electrons is so reduced that recombination is now largely between free holes and trapped electrons. 

The proposed mechanism of dye-promoted desensitization by oxygen is reaction of oxygen molecules with photoelectrons trapped by the dye (83), followed by reaction of the superoxide radical with a hydrogen donor or a mobile hole (eqs. 6 and 5). Desensitization increases with increasing depth of the electron traps provided by the dye. The deeper the trap, the longer is the time that an electron can remain in the trap and the greater is the probability that an oxygen molecule will have time to diffuse to the trap and react with the electron before the... 

A key assumption in the explanation of the high efficiency of the hole-injecting dyes is that the excess electron of the dye radical or an electron trapped from the conduction band by the ground state dye, if not removed by some secondary reaction, will eventually escape into the conduction band or will react with a silver ion. The effective depth of the trap—the energy required for the transfer of the electron to the conduction band... 

Steenken S, Jovanovic SV, Bietti M, Bernhard K (2000) The trap depth (in DNA) of 8-oxo-7,8-dihy-dro-2 -deoxyguanosine as derived from electron-transfer equilibria in aqueous solution. J Am Chem Soc 122 2373-2384... 

Fig. 6, and the results for numerous dopants in anthracene compared with calculated trap depths are given in Fig. 7. One notes that the general agreement is good considering the often approximate values of Ic and Ac available and also that particular impurities, notably tetracene, may function both as electron and positive hole traps of depths 0.17 eV and 0.42 eV respectively.

In the limit of large m (dilute crystals) this can be shown to approach AE = <52/12y5 already at m = 4 the value is within of this limit and at m — 6 within ff. The limiting formula may thus be used for all but the most concentrated crystals but it is valid only for a small compared with the least of the energy denominators, namely 1 — cos (2-npjm), so that it holds for a range of trap depths which narrows as the concentration measured by w-1 diminishes. However, in all situations the initial deviation from the unperturbed band is quadratic in the depth 8, just as has been shown for electron traps by Koster and Slater using a different argument. 

Let, for illustration, the depth of a discrete electron trap be Et, then the generation of singlets requires a thermal activation energy AE =Et — (Eg-Es) > 0, and... 

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