The change we are witnessing on a personal level such as the shift from using traditional bicycles and cars to electric bicycles and cars, and paper books to e-books shows the tremendous expansion of our dependence on electric energy in our daily lives. The same is true for the commercial and industrial sectors, and this explains expectations such as that the growth in demand for electrical energy will exceed the demand for other energy sources by two or more times .
Common methods of producing electricity through thermal power plants rely on resources like gas, coal, and oil that are produced over thousands of years by the sun’s effect on the breakdown of organic matter under the soil. The sun causes a temperature differential between two nearby places, which in turn causes wind, which powers turbines to produce electricity. As a result, the sun is the planet’s primary energy source, but to produce electrical energy, humans often need additional materials and energy sources.
The inability to directly transform solar energy into electrical power results in a number of environmental issues, including pollution, as well as economic issues since resources like oil are used more quickly than they are replenished in the environment.
Furthermore, transforming energy from thermal or mechanical sources to electrical sources first results in a large energy loss. Because of all of these advantages, photovoltaic PV technology—which is what we are familiar with thanks to solar panels—represents a true breakthrough in the economical and ecologically responsible production of power directly from light.
Photovoltaic (or solar) panel technology is the technique that uses semiconductors that experience the photoelectric effect to directly convert light into energy. This article will provide us with a basic understanding of the parts of the photovoltaic cell, which is the primary component of solar panels, as well as its operation and common terminology.
General principles
Before talking about the mechanism of action of photoelectric cells, we must recall the working principle of the components of these cells to understand how the photoelectric action occurs. The following explanation is very simplified because the aim of this article is awareness-raising and not research or academic.
Materials are generally divided into conductors, insulators, and semiconductors. The reason for the conductivity of conductive materials, like copper, is that the electrons in their final orbits have a weak connection, which makes it easier for the electrons to migrate to their atoms, for the electrons to float through the conductor, and for electric current to flow.
Conversely, no electric current flows through insulators because the electrons in materials like wood, for instance, remain firmly bonded to their atoms and are not transferred across them. Apart from these two categories of materials, there exist materials that are not thought to be good insulators and do not conduct electrical current well.
Certain materials, like silicon and germanium, do not readily shed their final orbit’s electrons; but, when these materials are exposed to specific environments, like elevated temperatures or doping, for example, their electrons become more mobile. We refer to these substances as semiconductors.
Semiconductors can be used in pure or similar form. For example, pure silicon can be used after purifying its crystals, or silicon can be doped with additional materials such as boron, resulting in a P-type semiconductor rich in positive holes, or silicon can be doped with materials such as phosphorus, resulting in an N-type semiconductor rich in negative electrons.
The process of connecting a positive P-type semiconductor chip with a negative N-type semiconductor chip forms what is called a diode or a PN junction. This connection is the main component of the photovoltaic electricity generation system.
You can go deeper into understanding the working principle of this connection, but what is currently important to us is knowing that this connection does not allow electrons to pass from the negative N-type chip to the positive P-type chip except through an electrical circuit if it obtains sufficient energy to cross the buffer zone between the two chips. That is, the electric current is generated and flows from the positive chip towards the negative chip.
Components of a photovoltaic cell
The adjacent figure “Simplified photovoltaic cell structure” represents a horizontal section of a photovoltaic cell whose main component is silicon. This cell consists of:
Structure of a photovoltaic cell
Absorber Layer: This layer absorbs photons from light directed at the photovoltaic cell. The main component of this layer is the pn-junction, which conducts the electrons and holes resulting from the photoelectric action.
Metal Front: This metal front is the outlet for the excited electrons that have transferred to the negative chip
Back contact: This contact receives the electrons that enter the positive chip and then merge with the positive gaps.
How a photoelectric cell works in a simplified way
Stimulation: The arrival of a photon from the sun to the absorption layer with sufficient energy leads to the stimulation of electrons and holes
Separation: The energy of the arriving photon may be sufficient to separate the electron from the gap, and it may be sufficient for the electron to move to the negative N-type chip and the gap to move to the positive P-type chip.
By applying a circuit to the photovoltaic cell, electrons leave the solar cell via the metal interface and return via the back conductor to merge with the abundant gaps in the positive foil. This movement generates an electric current in the opposite direction of the electrons.
By connecting photovoltaic cells in parallel and in series, we obtain solar panels (usually composed of 60 cells or 72 cells). The design of connecting the cells in parallel or in series and separating the cells into groups is done to determine the voltage and current of the solar panel, which is usually written on the sticker behind the cell.
Conclusion
This simple working principle has been used for decades in space applications and other specialized applications. The reason for the spread of this technology recently is that companies have achieved high conversion efficiencies and reduced manufacturing prices to make the electrical energy generated using these panels produced at prices competitive with traditional methods of generating electricity.
