Charge carriers holes

When the two ends of a material containing mobile charge carriers, holes or electrons, are held at different temperatures, a voltage is produced, a phenomenon called the Seebeck effect (Fig. 1.11). The Seebeck coefficient of a material, a, is defined as the ratio of the electric potential produced when no current flows to the temperature... 

Fig. 8-2S. Aoodic transfer reaction of redox holes with transport of mincnity charge carriers (holes) in an n-type semiconductor electrode il.r - anodic hole transfer current at an interface = limiting hole transport current i i = limiting diSiision current of redox partides.

Fig. 8-26. Cathodic iiyectian of minority charge carriers (holes) followed by recomlmation of minority charge carriers (holes) with majority charge carriers in an n-type semiconductor electrode ipr - cathodic current of hole transfer at an interface - current of electron-...

For p-type electrodes in the dark and in the photoexdted state, the concentration of majority charge carriers (holes) is sufficiently great that the Fermi level eptso of the electrode interior nearly equals the quasi-Fermi level of interfacial holes hence, the overvoltage Up sc for the generation and transport of holes in the space charge layer is zero even as the transfer of anodic holes progresses as expressed in Eqn. 10-30 ... 

The electrical conductance of semiconductors is derived from the mobility of charge carriers, holes h+ in the valence band and free electrons e in the... 

If an electric field is applied to the surface of the semiconductor from whatever source, the density of the mobile charge carriers (holes) is either enhanced or depleted, depending on the polarity of the field. If the field enhances the concentration of holes, the surface is said to be accumulated and the semiconductor surface behaves much as a metal, in that the excess charge appears at the surface and the electric field does not penetrate it further. 

In these systems the conductivity increases in the presence of oxidant gases that generate charge carriers (holes) and decreases by electron-donating gases which trap charge carriers [233], in a process in which the formation of five-or six-coordinate species seems to occur. 

Charge transport — When charged species move within a phase, this is called charge transport [i-viii]. Electron transport occurs in metals and -> semiconductors. (In the latter case the - charge carriers - holes, polarons, - bipolarons (- electronic defects) are also considered as moving charged species, while the superconductivity occurring at very low temperatures is explained by... 

Semiconductor electrodes whose band gap is relatively narrow receive photon energy and produce photoexcited electron-hole pairs in the space charge layer. The photoexcited electron-hole pair formation significantly increases the concentration of minority charge carriers (holes in the n-type), but influences little the concentration of majority carriers (electrons in the n-type). The photoexcited electrons and holes set their energy levels not at the electrode Fermi level, ef, but at what we call the quasi-Fermi levels, n p and p p, respectively. The quasi-Fermi level for majority carriers is close to the electrode Fermi level, F, but the quasi-Fermi level for minority carriers is far away from the electrode Fermi level. 

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