What is a semiconductor.

Good conductor (conductor): A substance which conducts electricity well
(Examples) iron, copper

Insulator: A substance which does not conduct electricity at all
Examples) wood, rubber

Semiconductor: A substance that is both a good conductor and an insulator; a substance which will conduct electricity given the right conditions.
(Examples) silicone, germanium, titanium oxide (TiO2)


Titanium oxide (TiO2)

Titanium oxide (TiO2)
Titanium oxide (TiO2) is a semiconductor, and when light hits, it releases an electron (anion).
This is called a photocatalyst reaction.

Photocatalyst reactions

What is a toothbrush and semiconductor ?