Solar cells are also called photovoltaic cells - or PV cells for short and can be found on many small appliances, like calculators, and even on spacecraft. They were first developed in the 1950s for use on U.S. space satellites. They are made of silicon, a special type of melted sand.
When sunlight strikes the solar cell,
electrons (red circles) are knocked
loose. They move toward the treated
front surface (dark blue colour). An
electron imbalance is created between
the front and back.
Construction of PV Panels - Source: Renewable Energy Trust
As seen in the science behind PV, a photovoltaic cell is created when a positively charged semiconductor is placed against a negatively charged semiconductor to create a diode. In practice, this semiconductor sandwich is combined with supporting materials to create panels that can then be arranged in arrays to provide different amounts of electricity.
Creating the Photovoltaic Cell
As seen in the science behind PV, a photovoltaic cell is created when a positively charged (P-type) layer of silicon is placed against a negatively charged (N-type) layer of silicon to create a diode and this diode is connected in a circuit via metal conductors on the top and bottom of the silicon sandwich. An actual PV cell includes these elements with an anti-reflective coating to accept more sunlight into the silicon sandwich.
1: The photovoltaic cell, a sandwich of two semiconductor materials. The cell reacts to solar energy and produces an electrical charge.
2: Metal conductor strips that run along the top layer of silicon. These strips capture the electrons freed when solar energy hits the cell and concentrate them into a current. Another metal panel, attached to the bottom layer of silicon, feeds electrons back into the cell.
An anti-reflective coating placed on top of or directly adhered to the silicon sandwich. This sheet reduces the amount of sunlight reflected off the glass allowing more sunlight to hit the cell and increasing the panel's efficiency.
Creating the Photovoltaic Panel
While the photovoltaic cell is the central element in a photovoltaic system, the photovoltaic panel is what we actually use to make a cell or group of cells usable. Once in panel form, photovoltaics can be used alone or in groups of panels to power many different electrical loads. Though different types of photovoltaics vary in their structure, they generally include the following elements:
1: The cell or multiple cells are the core of the photovoltaic panel.
2: A glass cover placed over the photovoltaic cell to protect it from the elements while allowing sunlight to pass through to the cell.
3: An additional plastic anti-reflective sheet is often used to enhance the effect of the glass cover and anti-reflective coating of the cell to block reflection.
4: A panel backing (typically plastic) and frame complete the photovoltaic panel, holding all the pieces together and protecting it from damage during installation.
Putting Panels in an Array
There are arrays of panels. These are created when multiple panels are connected together to form a larger circuit.