The key difference between valence band and conduction band is that the valence band exists below the Fermi level while the conduction band exists above the Fermi level.
Valence band and conduction band are closest to the Fermi level. These bands thus determine the electrical conductivity of solid materials. Fermi level chemical potential for electrons of a body is the thermodynamic work required to add one electron to the body.
CONTENTS
1. Overview and Key Difference
2. What is Valence Band
3. What is Conduction Band
4. Side by Side Comparison – Valence Band vs Conduction Band in Tabular Form
5. Summary
What is Valence Band?
The valence band is the electron band from which the electrons can jump out of when the atom is excited. Here, the electrons jump to the conduction band. Therefore, basically, it is the outermost electron orbital of an atom of any material which has electrons in it. Moreover, this term is closely related to the term “valence electron”.
What is Conduction Band?
The conduction band is a delocalized band of energy levels in a crystalline solid which is partly filled with electrons. These electrons have great mobility and are responsible for electrical conductivity. Here, the conduction band is the band of electron orbitals to which the electrons can jump when the atom is excited. These electrons jump from the valence band. When the electrons are in the conduction band, these electrons have enough energy to move freely inside a material. This movement creates an electric current.
Figure 01: A Diagram showing the Conduction Band and Valence Band
The bandgap is the energy difference between the highest occupied energy state of the valence band and the lowest occupied energy state of the conduction band. The bandgap indicates the electrical conductivity of a material. That is; a large bandgap means we need more energy to excite an electron (from the valence band to conduction band). And thus, the electrical conductivity is low.
What is the Difference Between Valence Band and Conduction Band?
The valence band is the electron bands from which the electrons can jump out of when the atom is excited. Meanwhile, the conduction band is a delocalized band of energy levels in a crystalline solid which is partly filled with electrons. The key difference between valence band and conduction band is that the valence band exists below the fermi level while the conduction band exists above the Fermi level.
Further, when an atom becomes excited due to the supply of energy, the electrons tend to jump into the conduction band from the valence band. It is because the conduction band is in a high energy state and valence band is in a low energy state.
Summary – Valence Band vs Conduction Band
The valence band is the electron band from which the electrons can jump out of when the atom is excited. But, the conduction band is a delocalized band of energy levels in a crystalline solid which is partly filled with electrons. So, the key difference between valence band and conduction band is that the valence band exists below the fermi level while the conduction band exists above the Fermi level.
Reference:
1. “Valence Band.” Valence Band – Energy Education, Available here.
Image Courtesy:
1. “Semiconductor band structure (lots of bands 2)” By File: Semiconductor band structure (lots of bands).png: Tim Starlingvectorisation: Mliu92 – file: Semiconductor band structure (lots of bands).png (CC BY-SA 4.0) via Commons Wikimedia