Here are the answers to your questions: 1. P-type semiconductors have extra holes which act as positive charge carriers. N-type semiconductors have extra free electrons which act as negative charge carriers. 2. In a solar cell, photons from sunlight knock electrons loose from the semiconductor material (e.g. silicon). This creates an imbalance between the n-type and p-type materials. The p-n junction acts like a diode, allowing the electrons to flow in one direction through an external circuit producing a current. 3. An inverter is important because photovoltaic cells produce direct current (DC) electricity but buildings use alternating current (AC). The inverter changes the DC

1. Energy & Environment

2. Noble Gas Electron
All elements want to have electronic Arrangement
arrangements like noble gases He (Helium) 2
Ne (Neon) 2,8
How do non metals and Ar (Argon) 2,8,8
metals achieve this? Kr (Krypton) 2,8,18,8
Non Metals share electrons. All the electrons get used
so there are no free electrons. Non metals are bad -
conductors. They are insulators.
Metals give electrons away. This provides free electrons.
Metals are good conductors of electricity.
-

3. The entire study of electricity is based on
the
Electron Theory
Electricity is a stream of electrons
flowing from one point to another.
- =

4. Explain why this ion has +11 charge
Cu 11+
Match these terms
to the figures
Molecule Atom Ion

5. Metals are good conductors of
electricity as electrons can move freely
-
Metal Ions

6. Noble Gas Electron
Arrangement
He (Helium) 2
Ne (Neon) 2,8
Ar (Argon) 2,8,8
Kr (Krypton) 2,8,18,8
How can it get this
arrangement?
It could share electrons with
another 4 silicon atoms...

7. Noble Gas Electron
Arrangement
He (Helium) 2
Ne (Neon) 2,8
Ar (Argon) 2,8,8
Kr (Krypton) 2,8,18,8
This is called a Silicon naturally wants an
Lattice electronic arrangement
like Argon

8. Lattice
Keeps bonding together
until something stops
them

9. That’s enough chemistry for just now.
Now lets have a look at energy

10. Energy Resources can be separated into 2 categories
NonRenewables Renewables
Consumed much faster than Always around us, are part
can be created of our natural environment
Run out Will not run out
Polluting Non-Polluting
Climate change Less reliance on other
sources/countries
Coal

11. Chemical Light
Heat
On a sunny day, the sun gives
off approximately 1,000 watts
of energy/m2 of the planet's
surface.
If we could collect all of that
energy, we could easily power
our homes for free

12. A solar panel is a made from many solar cells
A solar cell is a device that uses the photoelectric effect to
generate electricity from light.
The photoelectric effect is the flow of electric current in a
material when the material is exposed to light.
-
The simplest type of solar cell is made
from silicon which is a semiconductor

13. Non
Metals
Metals
Silicon is a Non
Metal

14. A semiconductor is between a conductor and
an insulator
Noble Gas Electron
What does an atom Arrangement
of silicon look like?
He (Helium) 2
Ne (Neon) 2,8
Ar (Argon) 2,8,8
Kr (Krypton) 2,8,18,8
Silicon naturally wants an
electronic arrangement
14x Protons like Argon

15. Pure Semiconductor
Noble Gas Electron
Arrangement
He (Helium) 2
Ne (Neon) 2,8
Ar (Argon) 2,8,8
Kr (Krypton) 2,8,18,8
So how can we make
a silicon lattice into a
conductor of
electricity?
By adding other elements to semiconductors
like silicon we can change its conductivity

16. Doping is the process of adding a tiny amount other elements
to a pure semiconductor such as silicon.
This increases its ability to conduct current as if effects the
electron arrangement of the lattice.
There are two forms of doping, p-type and n-type.
p for positive n for negative
Adding small amounts
of other elements to
improve performance

17. N (Negative) Doping
Adding an element with more electrons than are required
Extra Electron
Free to move about the lattice

18. P (Positive) Doping
Adding an element with less electrons than are needed
Missing Electron
A ‘hole’ for an electron has
been created

19. n-type
p-type and n-type (Negative)
semiconductors are Free electrons
used in solar panels
p-n junction
acts like a
diode. Allows p-type
electrons to (Positive)
move from P Missing electrons
to N side only -

20. Electric
current
produced
Sunlight loosens
electrons, creating
free electrons
Because electrons
are leaving the N-
-
type side, there are
spaces for the
electrons created
p-n junction forms
an electronic field. -
Acts like a diode.
Allows electrons to
move from P to N
side only

21. Photovoltaic Video

22. A solar cell can only
absorb 15-25% of the
sun's energy
Too much resistance inside the
semiconductor
If the photon doesn't have enough
energy, nothing happens
Silicon isn't as efficient at moving
electrons as a conductor

23. An array of solar panels are
Cells must be needed to produce enough
protected from power
damage and moisture
We use Alternating Inverter
Current (AC) in our
buildings as it’s Battery Direct current must
better at long be changed to
So we can use the alternating current
distance travelling
power when we want it so we can use it

25. Children are able to study
at night and women feel
safer going outdoors in
the dark
Portable solar
lights open up
opportunities for
many people in
rural areas.
This boy is able to charge
mobile phones off his
solar lamp and makes
money!
Runtime HIGH Setting: Up to 6 hours
Runtime LOW Setting: Up to 30 hours
Charge: 3-4 hours

26. Once installed they produce energy
without waste or pollution
They have no moving parts so
need little maintenance therefore
they are cheap to run
Solar power is good when grid
connection or fuel transport is difficult,
costly or impossible. e.g. satellites,
hilly areas, remote locations

27. Solar energy systems do not work in night
Solar cells need to be handled carefully so can
be difficult to transport
Solar cells are currently costly and
require a large initial capital investment

28. Type of light Efficiency Rated Durability Power
(Light Life consumption
intensity (Hours)
(lumens)/
watt)
Kerosene 0.03 Supply Fragile & 0.04-0.06
Lantern of dangerous liters/hour
kerosene
Incandescent 5-18 1000 Very fragile 5W
Compact 30-79 65000- Very fragile 4W
Fluorescent 15000
White Light 25-50 50000 durable 1W
Emitting
diodes (WLED)

29. p for positive n for negative
1. What is P-type and N-type semiconductors?
2. Explain how a solar cell works
3. Why is an inverter important in a
Photovoltaic System? DC to AC
4. Give 3x advantages of solar cells