Additional research topic resources

What are semiconductors?

When atomic or molecular building blocks are arranged in periodic structures, their orbitals can mix together to delocalize charge over longer range distances. As the number of molecular building blocks becomes very large the individual orbital energies become very close to each other and it is easier to refer to them as bands of orbitals rather than to each orbital individually. The mathematics to describe the behavior of these delocalized orbitals in periodic structures is referred to as band structure in physics.

Semiconductors are materials where there is a small but nonzero gap between the band of filled (HOMO) orbitals and the unfilled (LUMO) orbitals. This small gap allows for easy promotion of electrons from the HOMO to the more mobile LUMO levels with thermal or electrical energy to cause conduction, the concept behind the operation of logic gates in computers (i.e. transistors).

What are Organic Semiconductors?

Unlike conventional semiconductors such as silicon crystals which are made up of individual repeating silicon atoms, organic semiconductors have building blocks of molecules. Typically large Pi-conjugated molecules such as pentacene or unsaturated polymers such as polyacetylene. Charges can move through these delocalized pi-orbitals and the materials behave as semiconductors. This has lead to application in electronic devices such as solar cells, transistors, sensors, and LEDs.