A photoelectric cell, also known as a photocell, is a type of device that uses variations in light in order to change electrical properties such as current, voltage and resistance. According to Encyclopedia.com, photoelectric cells are currently used to create a wide range of items, including solar batteries, automatic door openers and burglar alarms.
The most basic variety of photoelectric cell consists of little more than two electrodes that are separated by a semiconductor with light-sensitive properties, states NASA. The electrodes of such a photocell are attached to a battery, which provides a steady level of current. This current, however, increases when the semiconductor is exposed to light. The greater the intensity of light, the greater the increase in current.
A more sophisticated type of photoelectric cell, known as a photovoltaic cell, is capable of generating current using light alone. In other words, no source of external voltage is needed. This allows the direct conversion of light into electrical energy. In other words, photovoltaic cells provide a means of harnessing solar energy. Photovoltaic cells are made up of two dissimilar materials that are separated by a semiconductor. When light hits the semiconductor, it generates a potential difference between the two sides. According to NASA, this is caused by electrons that are jarred loose from the semiconductor.