At the heart of any solar cell is the pn junction. Modeling and understanding is
very much simplified by using the pn junction concept. This pn junction results from
the “doping” that produces conductionband or valenceband selective contacts with one
becoming the n-side (lots of negative charge), the other the p-side (lots of positive charge).
The role of the pn junction and of the selective contacts will be explained in detail in
Chapters 3 and 4. Here, pn junctions are mentioned because this term is often present
when talking of solar cells, and is used occasionally in this chapter.