Thames & Kosmos Solar Mechanics handleiding

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Handleiding

load

(motor)

electron ﬂow

p-n junction

n-type layerp-type layern-type layerp-type layer

n-type layer

p-type layer

photons (sunlight)

contact layer

load

(motor)

electron ﬂow

n-type layerp-type layer

sun

electron

hole

free

electron

sun

load

(motor)

electron ﬂow

p-n junction

n-type layerp-type layern-type layerp-type layern-type layerp-type layer

photons (sunlight)

contact layer

load

(motor)

electron ﬂow

n-type layer

p-type layer

sun

electron

hole

free

electron

sun

interesting happens: electrons are able to move from the n-type layer into the

p-type layer, but not from the p-type layer into the n-type layer. This area where

the two layers meet is called the p-n junction. You can think of it like a hill,

where electrons can easily roll down the hill (to the p-type layer) but it is very

hard for them to go back up the hill (to the n-type layer).

cover glass

antiglare layer

top contact layer

n-type silicon

p-type silicon

bottom contact layer

→ →

third generation photovoltaic,

which does not use the tradi-

tional p-n junction at all. This

is a simpliﬁed description and

we encourage you to ﬁnd out

more about how solar cells

work from books, the internet,

and your science teacher.

3. Let there be light

When the cell is exposed to

light, the energy from the

light excites the electrons in

the p-type layer, and they

break free from their holes.

With contacts and wires at-

tached to conduct electrons

out of the p-type layer,

through a load (such as a light

bulb or motor), and back to

the n-type layer, we now have

a complete solar cell circuit.

4. The electrons ﬂow

When an electron moves, the

hole it was previously sitting

in becomes empty, and anoth-

er electron can easily move

into its position. And because

electrons can only travel in

one direction through the p-n

junction, they must pass

through the wire and load to

get back to the n-type layer.

This creates the electric

current.

This basic solar cell with one

p-type layer, one n-type layer,

and one p-n junction is called

a ﬁrst generation photovolta-

ic. A second generation photo-

voltaic has many layers and

multiple p-n junctions, to ab-

sorb more light. There is also a

CHECK IT OUT

Powering Up: Solar Cells | 17

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