Solar modules, also called photovoltaic (PV) modules, convert sunlight directly into electricity. They utilize semiconductor materials (e.g. silicon) similar to those used in computer chips. When sunlight is absorbed by these materials, the solar energy knocks electrons loose from their atoms, allowing the electrons to flow through the material to produce electricity. This process of converting light (photons) to electricity (voltage) is called the photovoltaic (PV) effect.
Amorphous silicon thin film PV modules are built by depositing a thin layer (less than one 10,000th of a cm) of silicon on top of a substrate, like glass. Such thin layer of deposited silicon films do not have any crystalline structure (pattern) and hence are called amorphous silicon films. Appropriate p-i-n junctions are made within this thin film by controlling the type and amount of doping (boron or phosphorus). Metal interconnects are used to bring the generated electric current out of the modules. Another sheet of glass encapsulates this thin film structure using an adhesive material. This glass-glass module is much like what is used in making windshields in the auto glass industry.
The performance of a solar module is measured in terms of its efficiency at converting sunlight into electricity. Only sunlight of certain energies will work efficiently to create electricity, and much of it is reflected or absorbed by the material that makes up the module. Because of this, less than about one-tenth to one-sixth of the sunlight striking the modules generates electricity. Historically, low efficiencies implied that larger arrays are needed, and that meant higher cost. Improving solar module efficiencies while holding down the cost per module is an important goal of the PV industry.
These modules generate DC electricity, which varies by the amount of sunlight falling onto the modules. In a typical solar installation connected to the electric utility grid, this DC output is converted into a regulated AC output by using commercially available inverters. In addition, a typical solar PV system includes module mounting structures, wiring, and power monitoring and metering devices.
