Properties of Semiconductors for Solar Cells

Semiconductors are a class of materials that have electrical conductivity between metals and insulators. Accordingly, their electrical characteristics can be controlled by doping and by light. They can be classified according to their chemical structure in elementary form, such as Si and Ge, in compound form, such as A3 B5 and A2 B6, or molecular form, such as the organic semiconductors or the perovskites, which are hybrid metal-organic molecules. All semiconductors have common distinguishing properties that govern their performance. The major properties controlling their electrical and optical behavior will be discussed in the next sub-sections. The first property is the atomic structure of the materials. It has a large
impact on their performance. There are three distinct atomic arrangements for any material:

1. Crystalline, where the atoms are perfectly ordered in a three-dimensional array
2. Amorphous, where the atoms of the material have random order compared with
   their original sites in the single crystal
3. Polycrystalline, where the material is composed of crystallographic grains joined
   together by grain boundaries.