Why and how does semiconductors conduct electricity when it receives light?

Answer 1

Because the light triggers emission of more electrons and thus ions in the semi-conductor.

Answer 2

When light hits a semiconductor (provided it is a suitable wavelength greater than the band gap of the semiconductor used) it has sufficient energy to excite an electron to a higher state leaving behind a 'hole'. These holes and electrons then drift across the material 'depletion region' towards the leads creating electricity.

if you want to understand it thoroughly then search for photo diodes on google. These are the main types of semiconductors used to convert light to power.

The 'Why' of the matter is that certain application primarily optics use light as a means of sending data. Thus once you propagate light through an optic fibre you need to receive it at the other end using means such as a photodiode.

Answer 3

when semiconductors are hit by light, mobile electrons are emitted which conducts electricity.But the degree of conduction depends on the wavelenght of the light incident on the semiconductor!