# Homework Help: Building a solar cell - semiconductors

1. Mar 27, 2012

### mathman44

1. The problem statement, all variables and given/known data

Design a solar cell, designed to absorb solar light. Treat the sun as a blockbody source of T=5800K.

To design the cell, you may grow 4 very thin semiconductors of the following bandgaps, in eV:

1.43, 1.14, 1.35, 0.67, 1.75, 2.4, 2.7, 0.42, 3.37

Which of these would you use, and in which order would you arrange them and why?

Of the semiconductors, which would you use, in which order would you arrange them, and why?

3. The attempt at a solution

Using wein's law the peak wavelength of the blackbody spectrum at 5800K is around 500 nm, which is 2.48 eV. The minimum is around 250 nm (4.96 eV), and the max is around 1800 nm (0.68 eV).

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So any semiconductor with a bandgap less than 2.48 eV will suffice to make electrons jump into the conducting band, similarily any semiconductor with BG less than 4.96 or 0.68 will suffice for the other extremes of the blackbody radiation.

I'm not sure how to put this together, any hints?

2. Mar 29, 2012

### JesseC

Intuitively do you think longer or shorter wavelengths travel further through materials? Thinking about that might help you with the ordering of the layers.

You are asking the right questions about the width of the solar spectrum and needing to choose a set of band gaps that cover this width effectively.