Question

Why are alkali metals used in photoelectric cells?

Answer 1

Alkali metals have lower ionization energy than their counterparts and hence have higher chance of emitting electrons when a radiation falls on them. So they are used in photoelectric cells so that they easily emit electron when energy containing photons in sunlight strikes them.

Answer 2

Alkali metals used to have low ionisation enthalpies and therefore, the electrons are easily ejected when exposed to light. Among alkali metals, cesium has lowest ionisation enthalpy and hence it can show photoelectric effect to the maximum extent and therefore preferred in photoelectric cell.