# What is quantum dot light?

##### 1 Answer

**Quantum dots** (QDs) are semiconductor particles, typically on the order of a few

The following is a simplified energy diagram for a quantum dot, showing its **band gap**, or HOMO-LUMO gap (more on the HOMO-LUMO gap is described here):

The idea is that applied electric fields will draw **electrons** (solid circles, **positrons** (dashed circles, *annihilate* each other, emitting photons (packets of light) as seen in the following nuclear equation:

#""_(-1)^(0) e + ""_(+1)^(0) e -> 2 ""_(0)^(0) gamma#

Or if you prefer, a diagram:

[Read more about this here.]

Depending on the dot **size**, they can be made to emit **different colors** of light; the wavelength emitted is *directly proportional* to the QD size.

This relationship can be seen by modeling semiconductors using the one-dimensional **Particle in a Box** energy levels:

#E_n = (n^2h^2)/(8m_eL^2)# where:

#h = 6.626 xx 10^(-34) "J"cdot"s"#

#m_e = 9.109 xx 10^(-31) "kg"#

#L# is the length of the "box".

#n = 1, 2, 3, . . . # is the principal quantum number.

So, since

Common applications for them are in transistors, solar cells, and quantum computing. You can find out how they are made by looking here.