A doped semiconductor is dipped into a solution of electrolyte. The electrolyte

Question

A doped semiconductor is dipped into a solution of electrolyte. The electrolyte solution contains a redox species with a mid-gap electrode potential. After absorbing a photon in excess of its bandgap energy, the photoexcited electron in the conduction band (CB) of a semiconductor moves spontaneously to the interface between the semiconductor and the liquid electrolyte. The hole in the valence band moves spontaneously away from the solid/liquid interface and into the bulk of the semiconductor. What is the correct statement about the doping of this semiconductor?

a. n-doped, since it has an excess of electrons the e- in the CB wants to escape.
b. n-doped, because there is an electric field generated at the interface that drives the electrons to the solid/liquid interface.
c. n-doped, because it has an excess of positive charges in the semiconductor at the solid/liquid interface, which attract the photoexcited electrons
d. p-doped, because there is an electric field that drives the electrons to the solid/liquid interface
e. p-doped, because it has an excess of negative charges in the semiconductor at the solid/liquid interface that attract the electrons.

Explanation / Answer

d. p-doped, because there is an electric field that drives the electrons to the solid/liquid interface

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