Photovoltaics

5.7 Photovoltaics

A photovoltaic or solar cell consists of a rectangular or round piece of metal covered with a thin, transparent layer of oxide as shown in Fig. 5.7.1 The light rays striking the oxide layer penetrates this layer and then the junction between the oxide and the copper. The light rays force the electrons to flow across the junction, and so generating electricity.

When the light rays are interrupted, the e.m.f. generated by them disappears at the same instant. A photovoltaic cell made of copper and copper oxide is very inefficient. Modern solar cells are made of silicon which is a semi-conductor. These are more effective than those made of copper, Fig. 5.7.2.

Photovoltaics are used in a wide variety of modern electrical and electronic devices. A few applications are:
(a) Spacecraft power supplies.
(b) Light meters.
(c) Automatic-operated switches.
(d) Burglar alarms.
(e) Cellphone chargers.
(f) Home lighting.

Although photovoltaics depend on light for their operation, exposure to heat may damage them.