PV explained and its components
A photovoltaic panel converts the sun radiation into electricity. This is achieved through solar cells, which are put together to a solar panel. The principal of the photovoltaic panels is based on the photo effect and was already discovered 1839 by Alexander Becquerel. At this stage the leading technology on the market is silicon based, with a market share of about 80%. The second most common technology with about 10% market share is thin film based, where of CdTe is the most common technology. That's why the focus of this Website will be on the crystalline solar panels.
1.1 Technology overview
Silicon based technologies
There are basically two different types, mono- and poly-crystalline. The raw material for both is silicon.
A boule is a single-crystal ingot produced by synthetic means. In the semiconductor industry, boules can be made by a number of methods, whereby the Czochralski process the most common one is, which result in a cylindrical rod of material. In the Czochralski process a seed crystal is required to create a larger crystal, or ingot. This seed crystal is dipped into the pure molten silicon and slowly extracted. The molten silicon grows on the seed crystal in a crystalline fashion. As the seed is extracted the silicon solidifies and eventually a large, cylindrical boule is produced. The efficiency of a mono-cell is about 20%.
For poly-cells the raw silicon is melted and poured into a form. The advantage of this technology compared to mono crystalline, that the process is not so time and energy consuming, but the price for it is a reduction of the efficiency, which lies for poly-cells at about 16%.
Thin film technology
There are many different types of technologies on the market, where off 3 common ones are listed below:
Amorphous silicon, this technology is often used for small tools like calculators. The efficiency is about 7%
CIS-, CIGS Solar cells (copper-indium-gallium-diselenide). Not very common but has for thin film a high efficiency of about 17,4%. The problem with this technology is the indium, which is expensive and limited.
CdTe-cells are cheap in production but only reach an efficiency of about 10% so far.
1.2 Build-up of a solar panel
The centrepieces of a solar-panel are the solar-cells. Normally a semiconductor crystal boule is cut with a diamond saw into circular wafers. In a following process the wafers are cleaned and receive a coating, which gives the solar cells their typical appearance. The thickness of a solar cell is about 0,2mm.
In the next step these cells are soldered together to a so-called string.
Which again are soldered together to a so-called matrix, which looks like the PV-Solar panel we know. Below you find a typical setup of a PV-Solar panel.