Build a PV Cell
_______________________
Name
Instructions
n-layer
1. The base of many photovoltaic (PV) cells is silicon (Si),
the same material that makes up sand. But this silicon is
very pure, which makes it expensive. Draw dots around
the Si atoms to remind you of the sand it comes from.
2. To make a PV cell work, the silicon has to have
impurities added. This is called doping. When
phosphorus (P) is added to the n-layer, it bonds to the Si
and has an extra electron left over. These electrons are
loosely held, and can be released by sunlight. Draw tiny
e’s or negative signs (-) around the phosphorus atoms
to show the extra electrons in the n-layer.
3. Boron (B) is added to silicon in the p-layer. When the
boron atoms bond with the silicon, there is a space for
more electrons. These spaces are like empty pockets or
holes that can hold electrons. Draw pockets (∪
∪) or holes
(o) around the boron atoms in the p-layer.
4. When sunlight shines on the n-layer, the electrons are
released, but they have nowhere to go! Fold this paper,
so the n-layer and p-layer can come together. The space
where the two layers touch is called the p-n junction.
5. Now electrons can flow from the n-layer to the p-layer,
but as more sun shines on the cell, the electrons build up,
and start to repel each other because they have the same
charge. A wire is needed to connect the two layers, so
the electrons can flow back where they came from.
Draw a line to show the wire connecting the two layers.
6. Because there is a current flowing through the wire, we
can make the solar cell do work, like spinning a motor.
Draw a circle on your line and put an “M” in it to show
where the motor could go.
7. Question: Why are there two wires on a PV cell?
Doped with Phosphorus
___________________________________________
___________________________________________
8. Question: Can a PV cell store energy like a battery?
Si
P
Si
Si
P
P
Si
Si
Si
Si
Si
P
Si
P
Si
P
Si
Si
Si
P
Si
Si
P
Si
Si
Si
Si
Si
Si
P
p-layer
Doped with Boron
Si
B
Si
Si
B
B
Si
Si
Si
Si
Si
B
Si
B
Si
B
Si
Si
Si
B
Si
Si
B
Si
Si
Si
Si
Si
Si
B
____________________________________________
9. Question: Can a PV cell make electricity in the dark?
___________________________________________
Created by Pat Higby
Higby@uni.edu
319-273-6012