PV or Solar Panels Construction Considerations 1

The principles on which a solar cell works and the main photovoltaic materials were reviewed, now lets review how a solar panel is made. The power and voltage that a single solar cell can provide is for most practical purposes very small, and even for application requiring very low power as in a handheld calculators the connection of more than one is necessary to provide sufficient voltage to power the electronic circuits, the connection of two or more cells are called photovoltaic panels or simple PV panels.

Because the voltage that a single cell can provide is in the range of 0.4V to 0.6V, several units need to be connected in series to obtain the desired voltage, at the same time if more current is necessary also several units need to be connected in parallel, in most solar panels a combination of series and parallel connections will be found. Depending on the power and voltage requirements and the power generation capacity of each individual cell, many arrangements of solar cells can be possible to meet the specified solar panel power requirements.

The Physical Solar Cell

The solar cell as any other electronic semiconductor device, (See solar cell principles) is biased, it has a positive and a negative side as in a diode, we might consider a solar cell as a flat diode. For this tutorial is be assume that our cells are of polycrystalline material due to it is low cost and high efficiency, making these very popular.

The most popular sizes of solar cells are (3 X 6) and (6 X 6) inches or about (7.62 X 15.24) and (15.24 X 15.24) mm respectively.

The glassy blue side of the cell with vertical

lines is the negative side

The mate dark color is the positive side of the solar cell.

As depicted on the figure, in the front or negative side are two vertical white lines, on the back of the solar cell is the positive side, they are two lines of three tabs each, some solar cells come with full lines instead of short tabs, in these line is were the tabbing wires are soldered to connect several cells. Some smaller cell could have only one line, while bigger could have three or more.

Transverse Cut of a Solar Cell

(Not to scale)

The above figure shows the transversal cut of a typical solar cell with the different layers that compose it, be aware that all these layers are in a thickness of only about half millimeter, therefore solar cells are very fragile and have to be handled with great care.

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Typical 3 X 6 Polycrystalline Solar Cell

Typical 6 X 6 Polycrystalline Solar Cell

3 x 6 Solar Cell Back

1- Back contact layer	5- Antireflection layer
2- Semiconductor type p	6- Transparent adhesive layer
3- Semiconductor type n	7- Glass
4- Front contact layer

The positive electrode line can segmented as shown here or continual