Solar panels represent the future of energy, yet the maximum recorded efficiency of a commercial solar cell is 33%, due to some molecular energy barriers.
Thomas Edison says: «I would like to invest my money in the sun and solar energy, what is the source of energy?! I hope we don’t wait until oil and coal run out before we deal with it.”
The whole world must now strongly agree that renewable energy is the only way forward to satisfy humanity’s energy needs. Greta Thunberg has tried to discuss this issue on numerous occasions before the leaders of the world’s most advanced nations. But it has been criticized by most world leaders, including US President Donald Trump. Experts know Greta is right, but when it comes to the greener energy alternatives i mentioned, each has its own limitations.
What if I told you that solar panels could solve the energy crisis?Wind speeds change dramatically, making it difficult to rely on them constantly. Dams can be built, but it is difficult to provide energy to the whole world. Sunlight is available free of charge during the day on most of the planet, so what’s the problem? Well, the maximum efficiency of the commercially available solar cell registered to date is 33.7%. This was one of the biggest challenges facing the solar industry, but why would there be such restrictions on the efficiency of solar panels? We’ll answer that, but first we have to understand exactly what the solar cell is.
What’s the solar cell?The solar cell is a device that captures energy directly from sunlight, and then converts it into electrical energy. The solar cell, also known as the PHOTOVOLTAIC cell, converts photons in light into voltage differences (which basically means electric power). To understand the limitations of the solar cell, we need to take a closer look at its composition.
Simple p-n linkSolar cells are made using n and p silicon chips, and silicon p has more holes, which means they lack electrons, while the n chip has excess electrons. The two chips are connected via the p-n link, which is the basic building block of the solar cell.
What does solar cell efficiency mean?Each device we use has a specific efficiency associated with it. Imagine, for example, a machine that produces 10 balloons per hour, of which two balloons are drilled. This means that the machine’s efficiency is 80%, because the machine absorbs the raw materials needed to produce 10 balloons, but only 80% of them are converted into useful products. The efficiency of the device is therefore the amount of useful output produced for each unit of input provided to it.
Energy gap between different materialsSimilarly, radiation falling on the entire solar cell does not turn into electricity. Only a limited part of that energy can be converted into useful products. There are many different measures of solar cell efficiency, the most common of which is the Shockly-Quaiser border.
What is the Shukla-Quaiser limit?The SQ, the most prominent measure of solar cell efficiency, measures the theoretical efficiency of a single solar cell under standard test conditions, the noon in the spring and autumn equinoxes in the continental United States, with the solar cell surface directed directly to the sun.
This is in addition to specific measurement criteria, such as the solar cell being made of only one homogenous type of material. There may be only one p-n link per solar cell, and each photon is supposed to have more energy than the (band gap) to convert into electrical energy (we’ll explain these terms later).
Why is there a limit to efficiency?The most important key step on which solar cell electricity generation depends is that electrons jump from the parity range (p-n link to the solar cell) to the conduction range (outer circle, such as battery). Electrons in a normal atom do not have supportive external energy in the parity range. To produce electricity, these electrons must be transferred to an external circle called the conduction range.
Light wave spectrumEquivalence range electrons don’t automatically jump into the connection range, but there must be a certain amount of energy, known as the range gap, so you can move.
Light wave spectrumThe incoming solar beam consists of waves at different wavelengths. The longest waves to the left (as pictured) are the weakest (with less energy), while the shorter waves to the right are the strongest. As such, only a few of these waves have the energy to overcome the energy barrier.
For example, imagine a photon beam of 100 different wavelengths, hitting a silicon solar cell, of which 40 have the equivalent of silicon’s band gap energy, and will then be able to produce electricity. The rest of the waves will dissipate in the form of heat or bounce off the surface of the cell. So there is a limit to the efficiency of the solar cell.
What other factors affect efficiency?As we’ve seen before, the e-transmission power threshold barrier has been found to be the main reason for the low efficiency of solar panels. But it is not the only factor, and then many other important elements.
The energy from the Sun is not the same energy that we receive here on Earth, because radiation travels through the dense atmosphere of our planet, reducing the phenomenon of light dispersion and refraction of its intensity, and preventing the ozone layer from reaching us. Therefore, these waves, which are able to cross the energy threshold, reach the surface to a limited degree, resulting in a further reduction in the efficiency of solar panels.
Is there a solution to the problem?Although most commercial solar cells currently available are only 33% efficient, the future looks bright. Researchers in pyrophosite materials and light emitting diode lamps at cambridge university have discovered that solar cells would become more efficient if their chemical composition became less demanding, i.e. by simplifying production processes and reducing costs.
Scientists around the world are working on newer materials, such as gallium nitride, germanium and indium phosvid. Many believe that these materials will effectively use the entire solar spectrum, turning it into electricity by changing the range gap limits of multijunction solar cells. The future generally looks bright for the solar industry.
ConclusionAustralian wildfires and amazonian forests have released huge amounts of carbon into the atmosphere, so much so that our planet may not be able to absorb it until 2050. Global warming is no longer only a future problem, it is a complete and undeniable reality. Environmentalists have exhausted all means to convince the world that green energy is the only way forward, yet some leaders still deny the truth.
The limited efficiency of solar cells is usually referred to as a reason why they are not used as a substitute for fossil fuels. The problem is that multinational companies and governments continue to invest large amounts of money in research and development in energy production from oil and coal, and ignore the development of safe alternatives. For example, materials with a lower range gap may be a possible solution to the problem at hand, but we need the world to pay attention to the importance of investing in this type of research.
What the world needs to understand and accept is that there is only one way forward if we want human beings to continue, it is a sustainable green way.