Platband Potentials

Flatband potential is a very important parameter for characterization of a semi-conductor/electrolyte interface as it correlates the band edges to the redox potentials in the electrolyte. It is most commonly determined by measuring the capacitance as a 

FIGURE 1.11. The fraction of the applied potential dropped over the space charge layer for dc conditions, Ydc. and for ac conditions, versus band bending with Ch = 1 XF/cm and Ni = 10 Vcml After Oskatn et ( 1998, Reprinted by permission of John Wiley Sons, Inc.) 

In an idealized case when the effect of the Helmholtz layer can be neglected, i.e., when Ch Csc, there is a negligible amount of surface states, that is. Css Qc. The total capacitance of the semiconductor/electrolyte interface described by Eq. (1.45) becomes C Csc. The interface capacitance as a function of the electrode potential then follows the Mott-Schottky equation  

A plot of 1/Csc versus potential V is linear and thus the potential where the line intersects the potential axis yields the value of Vn, and the slope yields the value of doping level N. The resulting flatband potential can be used to determine the potential of the conduction band edge Vcs. at the surface 

In practice, the determination of flatband potential according to the Mott-Schottky equation can be affected by a number of factors, e.g., high doping concentration (i.e., Ch Csc is not valid), the presence of a high density of surface states (i.e., 

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Ginley DS, Butler MA (1978) Platband potential of cadmium sulfide (CdS) photoanodes and its dependence on surface ion effects. J Electrochem Soc 125 1968-1974... 

Platband potential Haloge-Solar detoxification Titanium... 

TABLE 2.14. Platband Potentials of Silicon Materials Determined in the Dark in Various Solutions... 

FIGURE 2.31. Platband potential W of p-Si in MeCN as a function of redox potential Fredo of added redox ), be... 

Figure 5.21 Platband potential of n-GaAs in acetonitrile vs standard potentials of various metallocenes redox systems (after [37]).

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