- a solid-state device that converts light into electrical energy by producing a voltage, as in a photovoltaic cell, or uses light to regulate the flow of current, as in a photoconductive cell: used in automatic control systems for doors, lighting, etc.
- a device in which the photoelectric or photovoltaic effect or photoconductivity is used to produce a current or voltage when exposed to light or other electromagnetic radiation. They are used in exposure meters, burglar alarms, etc
