In electronics, a photovoltaic cell - or solar cell - is an electrical device that converts incident energy from solar radiation into electricity through the photovoltaic effect. Therefore, solar cells are the basis of photovoltaic systems to transform solar energy into electrical energy.
Compounds of a material that has a photoelectric effect absorb photons from light and emit electrons. When these free electrons are captured, the result is an electrical current that can be used as electricity.
Photovoltaic panels are made up of several groups of photoelectric cells connected to each other. Each group of photovoltaic cells forms a network of photovoltaic cells connected in series electrical circuit to increase the output voltage. At the same time, several networks are also connected in parallel circuit to increase the intensity of the electrical current that the device is capable of providing.
What Is a Photovoltaic Cell Like?
The most common solar cells are formed by a layer of crystalline silicon with a thickness of approximately 0.3 mm. The manufacturing process is of a sophisticated and delicate level in order to achieve a homogeneity of the material.
Silicon is currently the most widely used material in the creation of new photovoltaic cells. This material, which is the most abundant chemical compound found in the Earth's crust, is obtained by reducing silica. The first step is to create metallurgical silicon, 98% pure, from quartz stones derived from a mineral vein (the creation technique has nothing to do with sand).
Photovoltaic grade silicon must be transparent to 99.999%. To obtain this amount of purity, the silicon must be distilled into a special chemical compound. This special compound converts the distillate back into silicon.
The Positive and Negative Zones of the Solar Cell
The electric field is generated from the different polarization of two zones of the photovoltaic cell. Generally, the top part is negatively charged and the rest are positively charged to create the PN junction.
The P zone (positive zone or receptor anode) is a zone that lacks electrons and therefore has a positive charge. Generally, this configuration is achieved by adding a small part of boron that only has 3 valence electrons to pure silicon.
The N zone (negative zone or cathode or emitter) has excess electrons. Generally, this area is formed by the diffusion of phosphor that has 5 electrons in the last orbit.
Due to this difference in electric charge in the semiconductor material, the electric field in charge of pushing the electrons from the N layer to the P layer is produced.
The average conversion efficiency obtained by commercially available photovoltaic solar cells produced from monocrystalline silicon is lower than that of multilayer cells, typically gallium arsenide.
Currently there are also new technologies in the production of solar panels that do not use silicon.
How Does a Photovoltaic Cell Work?
If we connect a photovoltaic solar cell to an electrical circuit with a resistance (consumption) and at the same time it receives solar radiation, a difference in electrical potential will occur between its contacts. This voltage will cause the electrons to circulate through the charge.
Under these conditions, the photoelectric cell functions as a current generator.
Light is made up of photons that have a certain energy. When the light hits the solar cell, the photons hit the electrons in the N shell. If an electron absorbs the energy of a photon with sufficient energy, the electron is ripped from the material leaving a free space that another electron will occupy. This movement of electrons involves an electric current.
We can say that the current generated by an illuminated photovoltaic solar cell connected to a load is the remainder between its gross production capacity and the losses due to recombination between electrons and photons.
What Are Photovoltaic Solar Cells For?
Photovoltaic cells are the basic components of photovoltaic modules, which are solar panels capable of generating electrical energy from solar radiation. It is, therefore, the essential building block for this type of renewable energy.
A photovoltaic solar panel consists of a network of solar cells connected in series circuit to increase the output voltage. At the same time, several networks are connected in parallel circuit to increase the electrical current that the device is capable of providing.
The type of electrical current that a photovoltaic panel provides is direct current.
Photoelectric cells are also used to replace batteries in applications such as calculators, watches, gadgets, which can run on solar energy.
It is possible to increase its range of use by storing energy by means of a capacitor or a galvanic cell ( battery). When used with an energy storage device, a diode must be placed in series to prevent discharge from the system overnight.