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The figure below shows the absorption coefficient \(\alpha\) for amorphous and crystalline silicon. The figure also displays the solar irradiance of the AM1.5 spectrum due to photons with wavelengths lower than \(\lambda\).Which percentage of the solar spectrum does an a-Si:H layer of 300 nm thickness absorb? Remember that the AM1.5 spectrum has a total irradiance of \(1000W/m^2\). Hint: You can assume that the layer absorbs all photons with wavelength lower than that at which \(\alpha=1/d\). ______

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Silicon wafers can be p-doped by diffusing boron into the wafer. Imagine that boron is diffused into a wafer with no previous boron in it at a temperature of \(1100^oC \) for 5 hours. The diffusion can be described by the Fick's law, the same law studied in block 2.3, but for non-charged atoms in this case. The law gives us the diffusion flux \(J\) for a certain material with diffusion coefficient \(D\) and density gradient \(dn/dx\):\(J=D\frac{dn}{dx}\)If the concentration of boron at the surface is \(10^{18} cm^{-3}\), calculate the depth below the surface (in \(\mu m\)) at which boron concentration is \(10^{17} cm^{-3}\). The boron diffusion flux is \(310^{9} cm^{-2}s^{-1}\) and the diffusion coefficient for boron diffusing in silicon at \(1100^oC \) is \(1.510^{-12} cm^2/s\). ______

Why should the front n-layer of a c-Si solar cell be thinner than the p-layer?

A. The solar cell would actually have the same performance if the n-layer were thicker than the p-layer, as long as a p-n junction is created between these two.
Because the diffusion length of the photogenerated holes is larger in the n-layer than in the p-layer.
C. Because n-doping is required to absorb the incoming light.
D. Because most of the photons are absorbed close to the front surface of the solar cell and the thickness should be smaller than the hole diffusion length in the emitter.

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Which process involves dipping a seed crystal into a molten silicon liquid and pulling it upwards at a specific rotational speed?

A. Multicrystalline ingot casting
B. Float-zone pulling
Czochralski casting
D. Silicon wire casting

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Which of the following processes is used in order to fabricate monocrystalline silicon?Note that more than one correct answer is possible.

A. The Czochralski process
B. Fluid bed reactor process
C. The float-zone process
D. The Siemens process

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