The principle of a photovoltaic cell is the photovoltaic effect of semi­con­ductor materials. If light of a specific wave length (e.g. visible light 380 nm to 780 nm) is falling on the semiconductor, electrons inside the material are activated from their quiescent state. These electrons can now move freely inside the semiconductor material for a short time, until they are captured again by their quiescent state (recombi­nation). This effect is the so called photovoltaic effect.

In order to use the electrons generated by the photovoltaic effet as solar electricity, the electroncs must be directed to the interface of the semi­conductor before they fall back into their quiescent state again. This is achieved by selectively adjusting the electrical properties of the semicon­ductor. The adjustment is done by doping the intrinsic semiconductor with different atoms. If the resulting doped layers are stacked, the electrons flow to one interface of the stack. This stack represents the solar cell. If an external circuit is connected to both sides of the solar cell, the electron flow between the contacts results in a usable current.

The power generated by a single solar cell is not yet sufficient to supply a larger load. Therefore, the single cells are inter­connected to form a module. If one cell generates a power of 10 W, a module containing 10 cells generates a power of 100 W. Depending on the connection of the cells, the voltage and current of the module can be adjust­ed. Furthermore, connecting the cells to an encapsulated PV-module has the benefit to protect the sensitive cells against environmental effects. This hermetic sealing of the solar cells is one of the manufacturer's key know-how. The module has to withstand all environmental influences like wind and snow loads, water ingress must be prevented and the modules need to be mountable on the assembly system. 

Since a module is often not sufficient to provide the desired power, several modules are connected in series to a string. This string is then connected with the power grid by an inverter. If even greater system powers are required, several strings are connected in parallel.

Due to various reasons such as different areas of application, requirements for durability or even appearance, several module designs are available on the market. These modules differ especially in structure of the laminate, in which the solar cells are embedded. 

Glass-Foil-Laminate Modules:
The most popular type of modules. The solar cells are placed on a carrier foil. A front glass ensures the transparency and mechanical stability of the modul­es. Foil and front glass are laminated and framed by aluminum profiles. The back sheet foil allows the module to maintain a manageable weight. 

Glass-Glass Modules:
In case of higher mechanical loads or special applications glass-glass modules can be used. As the name suggests, the back of the module is also made of glass. This type has a higher specific weight, but the back glass increases the mechanical stability and ensures even longer durability of the modules. Manufacturers reward this with 5-10 years longer product warranty.

Laminate Modules without Frame:
Laminate modules can be used in projects with special requirements on the design of the system. These modules are sold without the aluminum frame. Laminate moduls allow incon­spicuous clamping of the modules which is particularly an advantage in case of building integrated systems.