Electron-hole recombination process

An important aspect of semiconductor photochemistry is the retardation of the electron-hole recombination process through charge carrier trapping. Such phenomena are common in colloidal semiconductor particles and can greatly influence surface corrosion processes occurring particularly in small band gap materials, such... 

Electron-Hole Recombination. A phenomenological representation of an electron-hole recombination process is shown in Figure 5. For illustration we assume that it is the electron that is the thermally-freed carrier although the discussion could just as well proceed on the basis that the hole is thermally liberated. 

It should be noted that in the above examples significant energy migration can occur between thermal stimulation and recombination since the electron is free to diffuse throughout the sample. Other electron-hole recombination processes occur, however, in which the excited states of the charge carrier are not to be found in the delocalized bands. An example of this, recently noted in the literature, concerns the TL emission from oligoclase feldspar in which the thermal stimulation involves the transition of the electron to a localized, intermediate state - see Figure 8... 

Figure 7. Thermoluminescence from CaF2 Ce following room temperature irradiation. The intense emission at low temperature is caused by electron-hole recombination processes as described in Equations (7-10). The emission at high temperatures is caused by vacancy-interstitial recombination. The spectrum of both emissions is characteristic of Ce + ions.

Figure 27 Molecular (D ), exciplex [(DA) — (A D )( T], charge-transfer (A -D+) excited species as generated by photo-excitation and electron-hole recombination processes in electron acceptor (A)-electron donor (D) molecular systems, hvD, hvEx, and hvEc are corresponding transition energies to the ground state, to be observed as different emission bands.

The spatial distribution of emitting species produced in the electron-hole recombination process is one of important reasons for a difference between the PL and EL spectra, and a characteristic determining the EL quantum efficiency. The self-absorption of the short-wavelength part of the fluorescence can be utilized for determining the spatial distribution of EL. The principle of the method, as discussed in Sec. 3.1 and used for photoexcited states in Sec. 3.2, has been adapted to the recombination radiation as follows [41] the unknown spatial distribution of the EL light intensity, if/ x) from a plate-shaped emitting sample, is related to the experimentally observed EL signal, El(Zo), by the expression... 

The surface of nanoparticles is of great importance for a number of device applications, since a number of surface defects, such as dangling bonds or deep surface traps and dislocations, determine the details of the electron-hole recombination process, a process which plays a crucial role in optoelectronic devices operation. The trapping of electron-hole pairs must be either sup-... 

The electron-hole recombination processes in the ion radical pairs P+B"H and P+BH across the A branch of the bacterial photosynthetic reaction center (RC) are taking place in the same molecular framework in which the primary charge separation occurs. Consequently, the rate constants for the recombinations are correlated to the rate constants of the primary processes, and their investigation can help in the elucidation of the primary charge separation mechanism. 

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