exercise questions Flashcards
How do you calculate frequency when given wavelength?
f=c/λ
What is the relationship between photon flux and light power density?
Φ=p/Epn
Epn= photon energy
How do you calculate current using photon flux?
I=ΦqA(QE)
where A = solar cell areas, q = charge of an electron and QE = quantum efficiency
How do you calculate open circuit voltage from reverse saturation current and short circuit current?
Voc = (kT∕q)ln(Isc/I0)
i0 = reverese saturation current
How do you calculate bandgap frequency of a material?
fg = qE/h
How is maximum efficiency calculated using bandgap frequency and light frequency?
η = fg/f
Why is shading such a problem for solar modules?
Shading just one cell in the module can reduce the power output to zero.
What equation is used to understand the relationship between the size of a quantum dot and its bandgap?
The bohr’s energy of a particle in an infinite potential well:
En = π²h²n²/2m*Lz²
How can the bandgap of quantum dots be tuned?
Altering their size.
What is the relationship between the size of a quantum dot and its bandgap?
The larger the bandgap. the smaller the quantum dot.
When do electrons become spatially confined?
When the diameter of a particle approaches the De Broglie wavelength of electrons in the conduction band.
What 3 kinds of mechanisms of a PV cell can quantum dots achieve?
- Hot carrier collection: increased voltage due to reduced thermalisation.
- Multiple exciton generation: more than one electron-hole pair per photon absorbed.
- Intermediate bands: quantum dots allow for absorption of light below the bandgap, without sacrificing voltage.
What are the advantages of dye-sensitized solar cells?
- Cheap and not energy intensive to manufacture.
- Can be produced on flexible substrates.
- Colour and transparency can be varied.
- Better than other solar cells in low-light intensity.
What are the disadvantages of the dye-sensitized solar cell?
- Requires improvements in cell/module efficiency.
- Poor performance in region of red light.
- Liquid electrolyte (freezing, expanding, volatility)
What are the advantages of perovskite solar cells?
- low cost + high efficiency
- Cheap and not energy intensive to manufacture.
- They can be produced on flexible substrates.
