A photovoltaic cell, also called a solar cell, is the main component that generates electricity in a solar panel. Photovoltaic is a term that relates to the production of electric current at the junction of two silicon semiconductors that are exposed to light (not necessarily sunlight) and it comes from the word "photo" meaning light and "voltaic" meaning electricity. When grouped together they form a solar module which can then be fitted into a frame to make a solar panel. The solar cells found in some calculators, in satellites, and even in Mars rovers are also called photovoltaic cells or panels. Any light that strikes a solar cell can cause a reaction inside it creating electricity. The most efficient light source would be the sun.
The parts of a solar cell are:
1. P-type Semiconductor
- This is a very thin layer comparable to the thickness of a paper or a card that is engineered to have loose and free moving positive particles called "holes". Just imagine this layer to be carrying positive particles wanting to bind with negative ones and that they keep moving until they find an opposite match.
2. N-Type Semiconductor
- This is basically the same as the P-type layer except that this one carries free moving "electrons". Imagine this one to be carrying negative particles that are also constantly looking for an opposite positive partner. This is also the part of the cell where the light passes through.
3. PN Junction
- This is a part of the solar cell that is created as soon as the P-type and N-type semiconductors are joined. This is where the electric field is created and separates the "holes" (positive) from the "electrons" (negative). This divider or junction is then affected when hit by light causing the particles to get excited making them move from each side of the divider.
4. Positive Conductor
- This is the layer located at the bottom of the P-type semiconductor and functions as a pathway for particles to move from P to N or vice versa. This is where the positive wire is connected.
5. Negative Conductor
- This also serves as a pathway for particles same as that of the Positive Conductor layer. This part of the solar cell is usually represented by the strips on top of the N-type semiconductor where the light is emitted. This is where the negative wire connects.
6. Anti-reflective layer
- Silicon can reflect an estimated 35% of sunlight and so a layer that can prevent this from happening has to be in place. This is the job of the anti-reflective layer where sunlight is emitted, effectively providing a better function for the semiconductors.
The way these parts work is very simple (but can be complicated in detail); the P-type holds the positive particles while the N-type holds the negative ones; they are then moved when light strikes the PN junction; the movement is then extended to the pathways which are the Positive and Negative conductors creating the electric current which when intercepted can be used to power electrical devices.
The solar cell can then be grouped to make a string that can also be grouped with similar strings creating a solar module that, when fitted into a frame, makes a solar panel, which, in turn, can be connected to other solar panels creating a solar array. Every time the cells are grouped, the output power increases, thereby powering more devices, and even up to a whole city. You are now well on your way to building the correct solar panel for home.
