What is photocel?

Answer 1

answer 2 A photocell is a device that converts light energy into electrical output.

From memory (?) selenium cells were the early photodetectors used on ancient photo equipment. (My Weston photo meter.)

It was not too difficult to improve on the selenium photocells.

Nowadays we are spoilt for choice for types of photocells, up to sophisticated photomltipliers, and solid state detectors that have completely replaced film for astronomy recording material.