Solids are materials whose atoms are bonded strongly enough to form a rigid structure; some solids have a random atomic arrangement with no particular pattern (called an amorphous solid, like common window glass), while others may have a very regular structure. A crystal structure is a solid with a unique arrangement of atoms that results in a pattern. This identification of crystalline materials will be important for understanding solar cell construction.
Crystal structures have the following properties:
- The patterns form a lattice, which is an array of points repeating periodically in three dimensions. In other words, the atoms form points in space that can be connected with geometrical lines to form repeating shapes.
- The patterns are recognized and separated as unit cells, which are just boxes surrounding a special arrangement of atoms in order to segment a pattern into its most basic form.
- The symmetries within these materials because of the repeating patterns allow us to easily identify some of the properties of special solids.
Semiconductors, which are an essential part of solar research, are materials that have a crystalline structure. This means that the covalent bonding in these materials is such that the atoms form a periodic atomic structure. This gives it some important electrical properties that we will see in later sections.
Source: Kopeliovich, Dmitri. “Crystal lattice examples”. Substech.com. 24 Feb. 2012.
Goetzberger, Adolf et.al. Crystalline Silicon Solar Cells. Chichester: John Wiley & Sons Ltd., 1998.