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 under 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 shortage (p-conductive layer). If two differently doped semiconductor areas convene, a so-called space charge region is created at the boundary layer (p-n junction).
In order to achieve the desired effect, the initial material is normally p-doped lightly and a thin surface layer heavily n-doped. This creates the space charge region required for separating charge carriers.
The front contact is a metallic grid, enabling the sunlight to penetrate into silicon between the contacts. Moreover, solar cells are also coated with an anti-reflection coating, serving to protect the cell and to reduce energy losses resulting from reflection. This layer gives the solar cells their typical bluish black appearance.
If sunlight hits 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 front surface and the positive charge carriers to the rear side electrode in the opposite direction.
The electron surplus in the n-silicon (negative electrode) and the electron shortage in the p-silicon (positive electrode) create an electrical voltage between the metal contacts on the front and rear side. For crystalline silicon cells, the electrical voltage at maximum power output is approx. 0.5V.
If the outer circuit is closed by connecting an electrical load, direct current will flow. Using a grid-connected inverter module to convert direct current (DC) to alternating current (AC), the electricity produced by the solar cells can be fed directly into the electricity grid.
