10.5
10.1
(a)
(b)
(c)
(d)
10.2
10.3
10.4
(a)
(b)
(c)
10.5
10.6
(a)
(b)
(c)
(d)
Exercises
Consider two solar cells: solar cell A has a bandgap energy of 1 eV and solar cell B has a bandgap energy of 1.7
eV. From all kind of possible losses, assume only optical losses. Which of the following statements is true?
Non-absorption losses are higher in solar cell A than in solar cell B.
Heating losses are higher in solar cell A than in solar cell B.
According to the Shockley–Queisser analysis, radiative recombination is more important in solar cell B
than in solar cell A.
According to the Shockley–Queisser analysis, solar cell A can have an efficiency up to 50%.
Consider an incoming monochromatic light beam of wavelength λ = 800 nm incident on a c-Si layer. How thick
should the layer be in order to absorb 90% of the incoming light? Assume the absorption coefficient to be
α(800 nm) = 10 3 cm −1 .
The typical thickness of the absorber layer of a c-Si solar cell is around 300 μm. Assume that the absorption
coefficient for infrared light is α(1, 100 nm) = 10 cm −1 . How much of the light with λ = 1100 nm is not
absorbed by the absorber layer? Give the answer as a percentage of the incident intensity I 0 .
Imagine that you are in the laboratory and can decide the thickness of the Si layer for your solar cell. You want
to optimise the solar cell performance for a wavelength of λ = 1, 000 nm, for which the absorption coefficient is
α(1, 000nm) = 10 2 cm −1 . For silicon, the minority carrier diffusivity is around D = 27 cm 2 /s and the minoritycarrier lifetime is around τ = 15 μs. Which thickness would you choose? (Hint: use the Lambert–Beer law (Eq.
(4.25).)
d Si = 100 μm.
d Si = 180 μm.
d Si = 300 μm.
In Figure 10.10 we have seen the absorption coefficient as a function of the wavelength for several
semiconductor materials. Let us consider monochromatic light of photons with energy E ph = 1.55 eV that is
incident in a film with thickness d. If we ignore possible reflection losses at the rear and front interfaces of the
film, what thickness is required to achieve a light absorption of 90% for the four materials?
A solar cell is illuminated by a light source that has an output power of 6 watts and emits monochromatic light
at a wavelength of 620 nm.
How many photons per second are emitted by the light source?
Assume that the solar cell converts all photons into electron-hole pairs and there are no recombination
losses. What current would the solar cell generate?
Assume that the electrons and holes do not lose any energy on their way to the contacts. What voltage
would the solar cell generate?
What would be the power conversion efficiency of the solar cell if it generated the current and voltage
calculated above? Can this be realised in practice?
10.1
(a)
(b)
(c)
(d)
10.2
10.3
10.4
(a)
(b)
(c)
10.5
10.6
(a)
(b)
(c)
(d)
Exercises
Consider two solar cells: solar cell A has a bandgap energy of 1 eV and solar cell B has a bandgap energy of 1.7
eV. From all kind of possible losses, assume only optical losses. Which of the following statements is true?
Non-absorption losses are higher in solar cell A than in solar cell B.
Heating losses are higher in solar cell A than in solar cell B.
According to the Shockley–Queisser analysis, radiative recombination is more important in solar cell B
than in solar cell A.
According to the Shockley–Queisser analysis, solar cell A can have an efficiency up to 50%.
Consider an incoming monochromatic light beam of wavelength λ = 800 nm incident on a c-Si layer. How thick
should the layer be in order to absorb 90% of the incoming light? Assume the absorption coefficient to be
α(800 nm) = 10 3 cm −1 .
The typical thickness of the absorber layer of a c-Si solar cell is around 300 μm. Assume that the absorption
coefficient for infrared light is α(1, 100 nm) = 10 cm −1 . How much of the light with λ = 1100 nm is not
absorbed by the absorber layer? Give the answer as a percentage of the incident intensity I 0 .
Imagine that you are in the laboratory and can decide the thickness of the Si layer for your solar cell. You want
to optimise the solar cell performance for a wavelength of λ = 1, 000 nm, for which the absorption coefficient is
α(1, 000nm) = 10 2 cm −1 . For silicon, the minority carrier diffusivity is around D = 27 cm 2 /s and the minoritycarrier lifetime is around τ = 15 μs. Which thickness would you choose? (Hint: use the Lambert–Beer law (Eq.
(4.25).)
d Si = 100 μm.
d Si = 180 μm.
d Si = 300 μm.
In Figure 10.10 we have seen the absorption coefficient as a function of the wavelength for several
semiconductor materials. Let us consider monochromatic light of photons with energy E ph = 1.55 eV that is
incident in a film with thickness d. If we ignore possible reflection losses at the rear and front interfaces of the
film, what thickness is required to achieve a light absorption of 90% for the four materials?
A solar cell is illuminated by a light source that has an output power of 6 watts and emits monochromatic light
at a wavelength of 620 nm.
How many photons per second are emitted by the light source?
Assume that the solar cell converts all photons into electron-hole pairs and there are no recombination
losses. What current would the solar cell generate?
Assume that the electrons and holes do not lose any energy on their way to the contacts. What voltage
would the solar cell generate?
What would be the power conversion efficiency of the solar cell if it generated the current and voltage
calculated above? Can this be realised in practice?