The Solar Panel Mystery Flaw, Explained
What Is The Mystery Flaw Found In Solar Panels?
As the world pivots more towards renewable energy, the demand for solar panels and solar power steadily increases. Though humans have only been utilizing solar panel technology as a society for about 40 years, the technology has steadily become more efficient and a more viable option to replace fossil fuels. When Charles Fritts invented the first working Selenium solar panel in 1883, it was only able to convert into voltage about 1% of the light energy that is absorbed. Today’s solar panels, however, are capable of converting about 20% of the light energy they absorb into usable electricity.
That is until just a few hours after they begin operating, at which point there is a drop of 10%, leaving them at roughly 18% efficiency. With a total of 630,000mw (MegaWatts) produced by all of the world’s solar panels annually, that 10% drop equates to about 30 nuclear power plants worth of energy. But what is it that causes this drop in efficiency? Can it be fixed? And the greater question beyond that is, if this defect can be fixed, how efficiently can the future of solar panels be made?
Understanding Solar Panel Technology
To understand why most modern solar panels lose 10% of their efficiency after operating for only a few hours, one must understand how solar panels are created and convert light energy into usable electricity (Voltage). The term for this drop in efficiency is “Light-induced degradation,” and scientists worldwide have been working on solving this issue for over 40 years.
When light hits a silicon surface, which most modern solar panels are made of, one of three things can happen: The light can be reflected, absorbed, and simply pass through the surface (transparent). When light energy is absorbed and generates a voltage and electrical current in a material, this is called the photovoltaic effect. In order to maximize the efficiency of the photovoltaic effect, scientists and engineers must first minimize the amount of light reflected. In untreated silicon, about 30% of the light hitting the surface is reflected, making the maximum efficiency of untreated silicon only 70%. However, there are ways to mitigate how much of the light hitting the silicon surface is reflected. For starters, silicon surfaces are often treated with silicon monoxide, which reduces reflection to about 10%. These surfaces are then treated again with titanium dioxide which can reduce reflection to as little as 3%. Lastly, if the silicon surface is textured, light that was originally reflected has a chance of being redirected, absorbed, and converted into voltage and an electrical current.
Powering A Solar Cell
To measure the energy of a photon, the equation E = F x H is used. Where H is equal to Planck’s Constant (4.136 ✕ 10-15 ) and F is equal to the frequency of the photon. In order to produce the photovoltaic effect in silicon, the photons must be absorbed into the material, but this requires above a threshold energy to increase an electron’s energy to move freely throughout the material. Silicon requires photons with 1.1eV (electron volts) to produce the photovoltaic effect. This corresponds to a wavelength of 1,110nm (nanometers). This means that because silicon can’t make use of light with a wavelength greater than 1,110nm, everything above this level is energy that can’t be converted into electricity. This represents about 19% of the total energy reaching Earth from the sun.
How A Solar Cell Works
Light energy strikes the surface, knocks an electron loose which creates a gap in the valence electrons. This free-flowing electron can then either fill that gap or be accelerated through the electromagnetic vault (depletion layer), which creates a potential difference (Voltage – The difference in electric potential between two points, which is defined as the work needed per unit of charge to move a test charge between two points.)
So What’s Causing The Solar Panels To Drop In Efficiency?
Many scientists and engineering had noticed that the drop was related to the concentration of Boron and Oxygen found in the silicon. It was also noted that this drop in efficiency did not occur when Boron was substituted for Gallium. From there, researchers worked out that the Boron-Oxygen defect was causing the issue. Others found that the defect could be reversed by heating the silicon in the dark at 200 degrees for 30 minutes. However, the defect would return once the silicon was reintroduced to the light. Efforts to fix this issue began focusing on reducing the Oxygen impurities introduces during the manufacturing of the silicon. It was found that these impurities would convert into something the scientists observing them called, ‘Shallow Acceptors’ when exposed to light. Essentially, they discovered that these impurities would form into little electron traps that act as recombination sites, which would reduce the time and probability of electrons entering the circuit to do work.
After 40 years of production, research, and heavy observation, scientists and engineers may finally be on their way towards creating a more powerful and more efficient solar cell capable of leading solar panels and solar power into the future.