Callister - An introduction - 8th edition

Chapter 21
Optical Properties
Load
(a) Schematic diagram illustrating the operation of a
photovoltaic solar cell. The cell itself is made of polycrystalline
silicon that has been fabricated to form a p–n junction (see
Sections 18.11 and 18.15). Photons of sunlight excite electrons
into the conduction band on the n side of the junction, and
create holes on the p side. These electrons and holes are drawn
away from the junction in opposite directions, and become part
of an external current.
(b) Photograph of a polycrystalline silicon photovoltaic cell.
(c) Photograph of a home that has a number of solar panels.
[(a) Photograph courtesy of Research Institute for Sustainable
Energy (www.rise.org.au) and Murdoch University. (b) Photograph
from http://commons.wikimedia.org/wiki/File:4inch_
poly_solar_cell.jpg. (c) Courtesy of iStockphoto.]
Sunlight
Photons
–
–
+
+
Electron
flow
“Hole”
flow
Current
p-type
silicon
(a)
n-type
silicon
Junction
(b)
(c)
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