A-Se is well developed technologically as it has been used as a photoconductor in photocopiers and also in an X-ray imaging technique known as xeroradiography for decades. It is used in its amorphous form, so amorphous selenium plates can be made by evaporation.

Why selenium is used in photoconductor?

Selenium is a good conductor of electricity in presence of light. This phenomenon is called photoconductivity.

Is selenium a conductor or insulator?

Selenium is a substance with an interesting property—it is a photoconductor. That is, selenium is an insulator when in the dark and a conductor when exposed to light.