Seminar 1

Question 1

What is the photovoltaic effect?

Answer 1

The creation of voltage and electric current in a semiconductor material upon exposure to light.

Question 2

When is a photon absorbed by a photovoltaic device?

Answer 2

When a photon has an energy greater than the bandgap energy of the light-collecting material in a photovoltaic device.

Question 3

What happens when a photovoltaic device absorbs a photon?

Answer 3

Electron-hole pairs are generated, which then diffuse to the depletion region where an electric field separates the electrons and holes, driving them through an external circuit.

Question 4

What is the depletion region?

Answer 4

An insulating region within a conductive doped semiconductor material where the mobile charge carriers have been diffused away or have been forced away by an electric field.

Question 5

How many generations of solar cells are there?

Answer 5

4.

Question 6

What is the most commercially popular generation of solar cell?

Answer 6

The first generation.

Question 7

What is the second generation of solar cells?

Answer 7

Thin-film technologies.

Question 8

What is the third generation of solar cells?

Answer 8

Cells using concepts allowing for more efficient utillisation of sunlight.

Question 9

What are some examples of second generation solar cells?

Answer 9

• Amorphous Silicon
• Polycrystalline Silicon
• Cadmium telluride
• Copper-indium-gallium-diselenide

Question 10

What are some examples of third generation solar cells?

Answer 10

• Sunlight concentrating solar cells
• Dye-sensitized solar cells
• Perovskites
• Polymer cells

Question 11

What are the advantages of first generation solar cells?

Answer 11

• Broad spectral absorption range

- High carrier mobility

Question 12

What are the disadvantages of first generation solar cells?

Answer 12

• They require expensive manufacturing technologies.

- Most photon energy is wasted as heat.

Question 13

What are the advantages of second generation solar cells?

Answer 13

• Low material costs
• Flexible/cheap substrates
• Reduced mass

Question 14

What are disadvantages of second generation solar cells?

Answer 14

• Toxic material (Cd)

- Scarce material (Te)

Question 15

What goals do third generation technologies pursue?

Answer 15

• Greater efficiency
• Abundant, non-toxic material
• Durability

Question 16

How do you calculate photon energy when given the wavelength?

Answer 16

Using the photon energy formula:

E=hc/λ

Question 17

How do you calculate a photons wavelength when given photon or bandgap energy?

Answer 17

Using a rearranged version of the photon energy formula:

λ=hc/E

Question 18

What is the photon energy formula?

Answer 18

E=hc/λ

where E is energy, h is Planck’s constant, c is the speed of light and λ is wavelength.

Question 19

How do you convert a quantity of energy in joules to electron volts?

Answer 19

Divide it by 1.602×10−19

Question 20

How do you calculate the wavelength of a blackbody when given its temperature?

Answer 20

Using the statement of Wien’s displacement law:

λmax(μm)=C/T
where c is 2987 and T is in kelvin.

Question 21

How do you calculate the temperature of a blackbody when given its wavelength?

Answer 21

By rearranging the statement of Wien’s displacement law.

Question 22

What is the statement of Wien’s displacement law?

Answer 22

λmax(μm)=C/T

where c is 2987 and T is in kelvin.

Question 23

What temperature is absolute zero in degrees Celsius?

Answer 23

-273.15

Question 24

How do you calculate total power density of a blackbody given its wavelength?

Answer 24

You must first use the statement of Wien’s displacement law to find the temperature, and then use the Stefan-Boltzmann law to find the total power density.

Question 25

What is the Stefan-Boltzmann law?

Answer 25

H=σT^4