Photodiode is A photodiode is a semiconductor device that converts light into electrical current. The current is generated when photons are absorbed in the photodiode. Photodiodes can contain optical filters and built-in lenses and have large or small surfaces.
Photocell is A device in which the photoelectric or photovoltaic effect or photoconductivity is used to generate a current or voltage when exposed to light or other electromagnetic radiation. They are used in exposure meters, burglar alarms, etc. Also referred to as: photocell or electric eye.
Structurally, it is common for photocells to be made of cadmium sulfide and photovoltaic cells of silicon.
“Photocell” usually means a light dependent resistor (LDR). It is a device whose electrical resistance changes with the amount of light available. Since resistors themselves do not generate any voltage or current, a separate power supply is required to use a photocell. They are typically used as a switch to turn a circuit on or off when the amount of light is above or below a preset level.
Photo cells generate a voltage or current that increases with the amount of light available. People often talk about solar cells that convert light into electricity when they talk about “photo cells.” A photo cell may also refer to a photodiode that outputs a small electrical signal that can be used as a measure of the light level.