An experimental study has been made of photovoltaic effects which occur at semiconductor‐electrolyte interfaces. Single crystal specimens of CdS and several other compounds were used. It was found that in a number of cases the photovoltaic effect results from a chemical reaction of the electrode materials. In such cases the observations may be explained by a simple mechanism which relates the sign of the photo‐emf to the conductivity type of the semiconductor and to the chemical reaction which is occurring. The reaction may be predicted using readily available thermodynamic data. A different process occurs when the electrode material is GaAs. It acts as an inert electrode which exchanges electrons with an oxidation‐reduction couple in the solution.

1.
E.
Becquerel
,
Compt. rend.
9
,
561
(
1839
).
2.
W. H.
Brattain
and
C. G. B.
Garrett
,
Bell System Tech. J.
34
,
129
(
1955
).
3.
H.
Gobrecht
,
R.
Kuhnkies
, and
A.
Tausend
,
Z. Elektrochem.
63
,
541
(
1959
).
4.
R. W.
Smith
,
Phys. Rev.
97
,
1525
(
1955
).
5.
J. E.
Baer
and
M.
Carmack
,
J. Am. Chem. Soc.
71
,
1214
(
1949
).
6.
R. H.
Bube
,
Proc. I.R.E.
43
,
1836
(
1955
).
7.
W. M. Latimer, Oxidation Potentials (Prentice‐Hall, Inc., Englewood Cliffs, New Jersey, 1952), 2nd ed.
8.
N. F. Mott and R. W. Gurney, Electronic Processes in Ionic Crystals (Oxford University Press, New York, 1948), 2nd ed., p. 69–74.
9.
Standard free energies of formation of ions in solution are reported with reference to an arbitrary zero in which ΔF0 for H+ is set equal to zero. For the purposes of this work absolute values of standard free energies of formation are required. Latimer (p. 22) reports a calculation of the absolute free energy change of a half cell reaction. This permits an estimate of the absolute free energy of formation of H+ ion in water to be +5 kcal/mole. This was used to correct Latimer’s reported values of ΔF0 of ions to absolute values. For positive ions the absolute value is obtained by adding 5 kcal/mole to Latimer’s reported value of ΔF0. For negative ions 5 kcal is subtracted from Latimer’s value. For neutral species no change is required.
10.
R. H.
Bube
,
Phys. Rev.
98
,
431
(
1955
).
11.
R. J.
Maurer
,
J. Appl. Phys.
16
,
563
(
1945
).
12.
American Institute of Physics Handbook (McGraw‐Hill Book Company, Inc., New York, 1957).
13.
R. Williams, Phys. Rev. (to be published).
14.
N. B. Hannay, Semiconductors (Reinhold Publishing Corporation, New York, 1959);
see Chap, 17 by J. F. Dewald.
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