What is a Solar Cell?
A solar cell is the colloquial term for a photovoltaic cell which converts solar energy into direct current electricity for use in homes or businesses through the photovoltaic effect.
- Solar cell and photovoltaic cell are synonymous.
- They are composed of several distinct layers that include both semiconducting and conducting materials.
- Maximum efficiency of typical solar cells on the market today range from 20-30%.
Understanding a Solar Cell
A solar cell is the colloquial term for a photovoltaic cell which converts solar energy into direct current electricity for use in homes or businesses through the photovoltaic effect. A collection of one or more solar cells are connected to make up a photovoltaic module, or solar panel. Each individual solar cell can typically produce up to 0.5-0.6 volts when properly optimized.
A solar cell is composed of several layers involved in the creation of electricity, each with a specific purpose. The most important layer is the semiconducting layer which actually has two distinct layers – one each of n-type and p-type silicon. These layers are what convert the sun’s energy into usable electricity through the photovoltaic effect. On the front and back of the solar cell are special conducting layers that collect the energy produced. These are the grid-like lines that can be seen on the front of a cell.
On the back side, the entire cell is able to be covered by the conducting layer, while on the front side, the conducting layer must only cover a very small portion of the cell so that it does not shade the semiconducting layer. Finally, there is an anti-reflection layer added to the cell. Naturally, all semiconductors are reflective which can cause a significant loss of solar energy if left alone, so a special coating is applied to reduce the loss of energy.
A solar cell’s efficiency is measured by the amount of electrical energy produced by the cell as a proportion of the amount of solar energy that hits the surface of the panel. This measurement tells us just how effective the solar cell is at converting the sun’s energy from one form to the other.
An important term in measuring the efficiency of a solar cell’s efficiency is the ‘bandgap’ of the semiconducting material. This term indicates the specific wavelengths of light that the material is able to absorb and convert. If the semiconductor’s bandgap matches the wavelengths of light shining on the PV cell, then that cell can make use of the available solar energy.
The reason that this is important is that about ¼ of all solar energy striking the Earth cannot actually be converted to electricity by the standard silicon photovoltaic panels that are on the market. This is due to the physics of how semiconductors work and how the photovoltaic effect generates electricity. Furthermore, any energy higher than the bandgap will end up being converted into heat, rather than electricity, and further reduces the efficiency of the photovoltaic cells.
And finally, of the electricity that is successfully generated by the cell, not all of it will actually make contact with the conducting material layer and will be lost. Because of all of this, the actual efficiency of a solar cell with current technology is only around 20-30%.
Photovoltaic Cell – A device that converts solar energy into direct current electricity for use in homes or businesses through the photovoltaic effect.
Solar Panel – The colloquial term for a photovoltaic module that uses sunlight to harness solar energy.
Photovoltaic Module – A collection of photovoltaic cells mounted together to collect sunlight for energy. Also, colloquially called a solar panel.