Question

which two statements correctly describe the role of a semiconductor in a solar cell?
a. when photons are absorbed, electrons from the semiconductor are freed because of the photoelectric effect.
b. when the semiconductors become charged, current flows from the positive one to the negative one.
c. when the semiconductors become charged, current flows from the negative one to the positive one.
d. the electrons freed from the semiconductors by light exit the cell and never return.

Explanation:

• Option A: When photons (light particles) are absorbed by the semiconductor in a solar cell, the photoelectric effect occurs. This effect frees electrons from the semiconductor atoms. This is a fundamental process in solar - cell operation.
• Option C: In a solar cell, when the semiconductors (usually a p - type and an n - type semiconductor) become charged (due to the separation of charges caused by the freed electrons), the current flows from the negative terminal (n - type semiconductor which has an excess of electrons) to the positive terminal (p - type semiconductor which has a deficiency of electrons). This is in line with the conventional current flow (opposite to the electron flow, but in terms of the movement of positive charge carriers in the external circuit, it is from negative to positive within the cell).
• Option B: Current flows from negative to positive within the solar cell (not positive to negative) when the semiconductors are charged.
• Option D: The electrons do not exit the cell and never return. In a solar - cell circuit, electrons flow through an external circuit and then return to the cell (in a complete circuit), usually through a recombination process.

Answer:

A. When photons are absorbed, electrons from the semiconductor are freed because of the photoelectric effect.
C. When the semiconductors become charged, current flows from the negative one to the positive one.