How it works - Take a peek inside solar power modules
Over 95 % of today’s solar cells consist of the semiconductor material silicon. Semiconductors are materials whose electrical conductivity increases with the influx of light or heat.
For the production of solar cells, the silicon is doped. For this purpose, other chemical elements are added, either creating an electron surplus (n-conductive layer) or an electron deficit (p-conductive layer). If two differently doped semiconductor areas convene, a so-called space charge zone is created at the boundary layer (p-n transition).
In order to achieve the desired effect, the initial material is normally lightly p-doped and a thin surface layer heavily n-doped. This creates the space charge zone required for separating charge carriers.
The front contact is a metallic mesh, enabling the sunlight to penetrate the silicon between the contacts. Moreover, solar cells are coated with an anti-reflection layer, serving to protect the cell and to reduce energy loss resulting from reflection. This layer gives the solar cells their typical bluish black appearance.
If the sunlight meets the solar cell, the impinging light particles (called photons) induce the formation of pairs of charge carriers, i.e. positive and negative charge carriers.
The electrical field of the space charge region separates these charge carriers. The electrons are accelerated to the negative electrode on the surface and the positive charge carriers to the rear side electrode in the opposite direction.
The electron surplus in the n-silicon (negative pole) and the electron shortage in the p-silicon (positive pole) create electrical voltage between the metal contacts on the front and rear side. For crystalline silicon cells, the electrical voltage at maximum output is approx. 0.5 V.
If the outer circuit is closed by connecting a consumer load, direct current will flow. Using a grid-controlled inverter module to convert direct current (DC) into alternating current (AC), the electricity produced by the solar cells can be fed directly into the electricity grid.
