PERC stands for Passivated Emitter and Rear Contact and refers to silicon solar panels. This not-so-new word in solar. It is an attempt to increase the utilization of solar cells. In fact, PERC is an additional layer on solar cells. PERC is just another technology to increase solar panel efficiency.
PERC, an extra p(layer) on the team
What does this extra layer actually do?
This additional dielectric passivating layer increases the solar cells’ ability to capture light by reflecting light (a photon) that passes through the solar cell without triggering electrons. By reflecting this light, the photons get more opportunities to generate electric current. These are wavelengths of light above 1180 nm that would otherwise be converted into thermal energy. Silicon wafers stop absorbing wavelengths above 1180 nm in normal solar cells.
What is the structure of a common solar cell, and how does it work? Read here
When the electron goes back to the solar cell through the back contact, it joins up with a hole again. This stops the flow of electricity for that pair. This process happens all the time when photons hit the surface of solar cells. In common situations, the normal way for traditional solar cells to make an electric current is for the electron-hole pair to recombine. However, there is another type of recombination called surface recombination that causes losses for traditional crystalline silicon technology.
When a hole joins with an excited electron that didn’t go through the contact, this is called surface recombination. The electron-hole pair joins without creating an electric current or solar power, so the solar cell is less efficient during this recombination process.
In addition to surface recombination, standard crystalline silicon solar panels can lose power because they aren’t good at capturing light, the solar cell itself reflects light, and materials in the module partially block light. Researchers in the solar business came up with the PERC solar cell to cut down on efficiency losses.
How does PERC start ? A very brief history
PERC technologies, which first occurred in 1989, are modified silicon cells with an extra layer on the back. This extra layer can send light back across the n-type and p-type junctions to make more energy because it is reflective.
Plus, this reflective covering helps lower rear recombination and keeps longer wavelengths from turning into heat that would slow the cell down otherwise. Early industrial applications of PERC technology had issues, primarily because light damaged them more quickly. But thanks to steady improvements over the years, PERC modules can now produce more electricity from the sun than standard silicon modules.
When solar PV technicians use the newer PERC standard, they can save time and money this way. This is because fewer solar cells are needed to make the same amount of power. A smaller number of panels also means fewer racks, wires, and MLPE devices are needed to link everything.
PERC parts and comparation with standard Si cells
A normal crystalline silicon (c-Si) solar cell has two layers that are electrically different from each other. The name for these two parts is “base and emitter.” The interface is the place where the base and receiver meet. When two layers meet, an electric field is created. This spot is known as the interface. Negatively charged electrons are pulled into the emitter. Electrons are taken away from the silicon atoms when light comes into the solar cell. After the electrons are set free, they can move through the silicon chip as they please. The electrons will only add to the electric current, though, if they get to the point where the emitter and base meet.
Jump with PERC over the 20%
The dielectric surface passivation in PERC technology lowers the amount of electron surface recombination. With the PERC solar cell, the area of touch between the semiconductor and metal is reduced, and the rear surface reflection is increased by adding a metal reflector that is moved away from the semiconductor. This lets photons enter or leave the cell and absorb them, but it also stops heat from absorbing them. In standard silicium cells, this increase is about 1%, just enough to jump over 20%.
Shoult we buy ?
- PERC is just another technology to increase solar cell efficiency. It could be combined with other technologies to increase efficiency (bifacial and interdigitated back contact technology).
If we want to buy panels, we should consider parameters such as power, efficiency, and price. It is good to use PERC in our panels, but it is not crucial.
And here are some interesting links about PERC technology if you want to investigate