A photovoltaic (PV) module is composed of solar cells. These solar cells are connected in series and/or parallel to obtain the desired electric power output from the module.
PV module arrays are made up of several PV modules, which themselves are composed of multiple solar cells.
In a module, the solar cells are electrically connected and placed between two very thin transparent layers of encapsulation material. This material is then placed on top of a reflective backing sheet (commonly made from polyvinyl fluoride), and sealed with a glass cover in an aluminium frame. These layers of material protect the solar cells from the environment and ensure that moisture does not enter the module. In lower quality PV modules water may penetrate the layers, which is one of the most common causes of module degradation. Electrical output contacts are in a junction box at the back of the module where the cables are attached.
When the surface of a solar cell is exposed to light, photons fall onto the cell and are absorbed. The energy from these photons is transferred to the electrons in the cell, causing them to become mobile. When these electrons are channelled together to run through a metal cable, they produce direct current (DC) electricity.
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