The light dependent diodes include Solar cell, which is a normal PN junction diode but has its conduction by the rush of photons which are converted into the flow of electrons. This is similar to a photo diode but it has another objective of converting maximum incident light into energy and storing it.

The figure below represents the symbol of a solar cell.

A solar cell has its name and symbol indicating storing of energy though it is a diode. The feature of extracting more energy and storing of it is concentrated in the solar cell.

Construction of a Solar cell

A PN junction diode with an intrinsic material in the deletion region is made to encapsulate in a glass. The light is made to incident on maximum area possible with thin glass on the top so as to collect maximum light with minimum resistance.

The following figure shows the construction of a Solar cell.

When the light is incident on the solar cell, the photons in the light collide with valence electrons. The electrons are energized to leave the parent atoms. Thus a flow of electrons is generated and this current is directly proportional to the light intensity focused onto the solar cell. This phenomenon is called as the Photo-Voltaic effect.

The following figure shows how a solar cell looks like and how a number of solar cells together are made to form a solar panel.

Difference between a Photo diode and Solar cell

Photo Diode works faster and concentrates on switching rather than providing more power at the output. It has a low capacitance value because of this. Also the area of incidence of light energy is lesser in Photo diode, according to its applications.

A Solar cell concentrates on delivering high output energy and storing the energy. This has high capacitance value. The operation is a bit slower than photo diode. According to the purpose of the solar cell, the area of incidence of light is larger than photo diode.

Applications of Solar Cell

There are many applications for Solar cell such as −

Science and Technology

• Used in Solar panels for Satellites
• Used in telemetry
• Used in Remote lighting systems etc.

Commercial Use

• Used in Solar panels for storage of electricity
• Used in Portable power supplies etc.
• Used in household uses such as cooking and heating using solar energy

Electronic

• Watches
• Calculators
• Electronic Toys, etc.

Some diodes emit light according to the voltage applied. There are two main types of diodes in this category. They are LEDs and Laser diodes.