Selenium conducts electricity better in the light than in the dark

[Phy6explorer]

I was reading an article about Selenium and I found that Selenium conducts electricity better in the light than in the dark. Why is that so.And is that why they are used in photocells?

 

[Gokul43201]

Yes, the reason is the same. Selenium is a direct gap semiconductor with a band gap (if you are not familiar with any of these terms, make sure you look them up) of about 2eV, which is right in the middle of the range of visible light. In the dark, the conduction band is essentially unoccupied, but when light is incident on it, electrons get excited to the conduction band, providing the ability to conduct electricity.

 

[Phy6explorer]

But what do you think will happen if I pass electricity through selenium in the dark? I guess that most of the electricity will not be conducted but what will happen to the rest?

 

[Gokul43201]

The same thing that happens with any insulator.

There are some very basic concepts you need to learn first. I suggest you start with Ohm's Law and understand the concept of resistance. Then you can try to understand what conductors and insulators are.