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The direct conversion of sunlight into electrical energy using solar cells is called photovoltaic.

Up to now these cells have generally been made out of the semiconductor silicon. With the appropriate treatment, various layers are created that produce an electric field, which separates positive and negative charges as soon as light falls on the solar cells. The charges remain available for use at the two poles of the solar cell, as in the case of a battery. The solar-generated direct current can be used directly to power electrical equipment, or be stored in batteries. Alternatively, the electricity can be transformed into alternating current with an inverter and fed into the electricity grid. In order to create larger output units, many solar cells are combined and interconnected in a solar module.



Function diagram of a solar cell:

1. Negative electrode
2. Positive electrode
3. n-type silicon
4. p-type silicon
5. Boundary layer
 
Photovoltaic systems have a great advantage in that they can be operated anywhere, independently of the electricity grid. Connecting them to a battery turns them into stand-alone systems, in which the solar electricity is directly used or temporarily stored. If too little sunlight is available, e.g. at night, electricity can be drawn from the battery and used. Common applications of these systems are small solar home systems for lighting, or powering a radio or TV set, in individual buildings. However, stand-alone systems can also be installed to cover village electricity supplies, for example where several houses are connected via a small electricity network. In these cases, it makes sense to transform the solar-generated direct current into alternating current so that standard appliances can be operated.

In nine of ten solar systems, this is based on silicon technology. Silicon is gained from quartz sand in several melting and cleansing steps. The liquid silicon is cast into blocks. These blocks (ingots) are cut into thin discs, the so-called wafers. Refine will use these wafers and processes them into solar cells. To this end the wafers are cleaned with acids and alkaline solutions and electrophysically altered. Finally an anti-reflection film made of silicon nitride is applied to them to increase their efficiency. In a last step the electrical contacts are attached. Q-Cells sells the finished cells to solar module manufacturers.