Quantum efficiency factor

For a simplified case, one can obtain the rate of CL emission, =ft GI /e, where /is a function containing correction parameters of the CL detection system and that takes into account the fact that not all photons generated in the material are emitted due to optical absorption and internal reflection losses q is the radiative recombination efficiency (or internal quantum efficiency) /(, is the electron-beam current and is the electronic charge. This equation indicates that the rate of CL emission is proportional to q, and from the definition of the latter we conclude that in the observed CL intensity one cannot distii pish between radiative and nonradiative processes in a quantitative manner. One should also note that q depends on various factors, such as temperature, the presence of defects, and the... 

In electroluminescence devices (LEDs) ionized traps form space charges, which govern the charge carrier injection from metal electrodes into the active material [21]. The same states that trap charge carriers may also act as a recombination center for the non-radiative decay of excitons. Therefore, the luminescence efficiency as well as charge earner transport in LEDs are influenced by traps. Both factors determine the quantum efficiency of LEDs. 

Direct Photolysis. Direct photochemical reactions are due to absorption of electromagnetic energy by a pollutant. In this "primary" photochemical process, absorption of a photon promotes a molecule from its ground state to an electronically excited state. The excited molecule then either reacts to yield a photoproduct or decays (via fluorescence, phosphorescence, etc.) to its ground state. The efficiency of each of these energy conversion processes is called its "quantum yield" the law of conservation of energy requires that the primary quantum efficiencies sum to 1.0. Photochemical reactivity is thus composed of two factors the absorption spectrum, and the quantum efficiency for photochemical transformations. 

SN)X can act as an efficient barrier electrode in ZnS junctions, increasing the quantum efficiency of the blue emission by a factor of 100 over gold.14 It can also be used to increase the efficiency of GaAs solar cells by up to 35%. Metal ions interact more strongly with a poly(sulfur nitride) surface than with other metal electrodes. This property has stimulated investigations of possible applications of (SN)X as an electrode material. 

Currently used nonlinear optical crystals are potassium dihydrogen phosphate (KDP) and barium borate (BBO). Compared to KDP, the advantages of BBO are its transparency in the UV and its larger quantum efficiency of up-conversion by a factor of 4—6. For a given position of the crystal, only a narrow band of the fluorescence spectrum is up-converted. Therefore, if the full fluorescence spectrum is of interest, the crystal must be rotated at a series of angles. An example of experimental set-up is presented in Figure 11.2. The fwhm of the response is 210 fs. 

It is important to recall that the virtual levels in Figure 1.16 do not correspond to real stationary eigenstates of our quantum system. As a result, Raman spectra are much weaker than fluorescence spectra (by an efficiency factor of about 10 -10 ),... 

Conseqnently, the efficiency is reduced by a factor of 57.5 % with regard to the quantum efficiency of the dilnted system. 

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