Solar modules, also known as photovoltaic (PV) modules or solar panels, are the core components of a photovoltaic system. They consist of several solar cells connected in parallel or in series. These cells produce electricity from the incident solar radiation.
The exact designation of solar modules results from how their individual solar cells are constructed. These cells consist of a semiconductor material - either monocrystalline or polycrystalline. A monocrystalline cell is made from a single (therefore: mono) semiconductor crystal. Its artificial cultivation is relatively complex and the cells are therefore more expensive than polycrystalline cells. However, monocrystalline cells have a better efficiency. This means that they produce more electricity from the same amount of solar radiation. Their maximum efficiency is 22%. Polycrystalline cells, on the other hand, are made up of several (hence: poly) crystals. They are cheaper to produce, but have a lower efficiency than monocrystalline cells. Their maximum efficiency is 20%. This difference may seem insignificant, but it can be important if the roof area for the photovoltaic system is limited.
In the solar module, the cells are protected against environmental influences by a film and an overlying glass pane facing upwards. Since these two layers are transparent, the sun's rays can pass through them unhindered and reach the cells. To ensure that the back of the modules is also protected against environmental influences, there is either a glass pane or a film on the back. Accordingly, we speak of glass-glass modules or glass-foil modules.
The luminous efficacy and thus the amount of electricity produced can be increased by about 1% with PERC technology. PERC stands for Passivated Emitter and Rear Cell (often also: Contact). Modules with this technology are called PERC modules. They differ from standard cells in their structure by two additional layers.