Direct Energy, 2018a

138 6.8 Problems
6.6. Use Fig. 6.6 to answer this question.
(a) Suppose you would like to make an LED that emits red light with
a wavelength of 650 nm. Suggest three possible semiconductor
materials that could be used.
(b) Suppose you would like to make a layered solar cell using layers
of the following materials: InP, In 0.5 Ga 0.5 As , and AlAs 0.5 Sb 0.5 ,
Which layer would be on top, in the middle, and on the bottom
of the device, and why?
6.7. Use Fig. 6.6 to answer this question.
(a) Find the energy gap of InP 0.1 As 0.9 in the units of joules.
(b) If InP 0.1 As 0.9 is used to make an LED, nd the expected frequency,
in Hz, of the photons emitted.
(c) Would it be better to make a solar cell out of gallium phosphide
or indium phosphide? Why?
6.8. A solar panel produces an average power of 800 W. The panel is in a
location which receives an average of 0.07 cm W of optical energy from
2
the sun. Assume the panel has an eciency of 9%.
(a) Calculate the surface area of the solar panel in units m 2 .
(b) Calculate the average amount of energy (in eV) produced in one
week.
6.9. A solar panel has an area of 50 m 2 , and it produces an average of 4
kW of power. The panel is in a location which receives an average of
0.085 cm W of optical energy from the sun. Calculate the eciency of
2
the panel.