When talking about solar panels, efficiency is an important part of the conversation these days.
Technologies are created or improved in order to address the increasing need for higher harnessing rates of solar energy using the minimum amount of space.
Some of those technologies involve changing the solar cell design from scratch, others just try to adjust things a little bit to improve the properties of solar modules.
The PERC cell is one of those that improve the characteristics of solar panels and is one of the most recently and rapidly adopted technologies. It is also expected to grow significantly over the next few years, as the most important solar cell technology among silicon cells to be manufactured by 2025.
But, what does the PERC acronym stands for and why should you care about it?
What Does PERC Mean?
The definition of the acronym actually varies depending on the author that you are consulting, you may find it as Passivated Emitter Rear Cell or Passivated Emitter Rear Contact.
Probably the name did not clarify many things, but, here is a clear and simple explanation.
What Is The Difference Between A Standard Silicon Cell And PERC?
In order to understand the difference, you should first understand the composition of the standard silicon cell.
It consists of the following layers:
- Screen printed silver paste (contacts of the cell)
- Anti-reflective coating
- Silicon wafers that form the P-N junction from phosphorus and boron doping
- Aluminum Back Surface Field (Al-BSF)
- Screen aluminium paste.
Because of its characteristics, the traditional technology is often referred to as Al-BSF and is the standard basis for most panel manufacturers around the world.
Under this configuration, the photons (light particles) that reach the surface of the cell have three options: to be absorbed, reflected, or transmitted.
The absorbed photons release electrons and make electricity flow.
Reflected photons are considered a loss as they do not contribute to the generation of electricity. This loss can be reduced by the use of antireflection coatings.
Transmitted photons are also considered a loss because they just pass through the cell and don’t generate electricity. Such a loss can reduce the efficiency of the solar cell.
Here is what a screen-printed solar cell looks like:
PERC solar cells try to address the losses related to the transmitted photons.
The upfront side of the cell is identical to an Al-BSF cell, but when you take a look at the rear surface you find a passivation film (or dielectric layer) with tiny pockets or holes in the film that allow the transmitted photons to be reflected back to the silicon layer for a second chance to get absorbed.
This increases the number of photons that release electrons in the solar cell and generates more electricity.
Here is a PERC cell structure:
What Are The Benefits Of The PERC Cells?
- The PERC technology can be applied to either polycrystalline or monocrystalline wafers.
- It increases efficiency values by up to 25% in solar modules, which is one of the highest values of the industry.
- Manufacturing procedures are not much different from traditional solar cells as only the rear surface is modified by simply adding a dielectric layer and using lasers to open the holes. This means the solar panels have a higher energy output with little investment and few risks.
- Short circuit currents and operating cell voltages increase and therefore power outputs as well.
- Reflectivity is increased up to 90-95% instead of the 65% of typical configurations.
- PERC cells perform well under high temperature or low-light conditions.
- The cost of the PV system installation can be reduced as fewer panels may be needed to achieve the same energy outputs than traditional panels.
Which Popular Solar Brands Support The PERC Technology?
- Canadian Solar
- Trina Solar
- REC Solar
- Jinko Solar
PERC & Light-Induced Degradation
However, there also are some challenges for PERC technology. For example, light-induced degradation (LID) is a significant challenge, particular for polycrystalline PERC. Watch the video below to get more insights from solar industry experts:
PERC technology is not really new. Actually, the first development of the concept came from the University of New South Wales (yes, here in Australia!) in 1983, but it was not until recently that it became commercially viable. Taking advantage of this fact, it is now the time for PERC cells to shine!
The efficiency values of PERC technology has reached 25% (in the UNSW), the number that has driven increased interest in the industry because the concept is not too different from traditional solar cells, meaning reduced implementation costs in the manufacturing process.
Moreover, the whole technology can be summarized as a way to increase the reflectivity of the rear surface of the solar cell, increasing the number of photons that can be absorbed and translated into more electricity production.
The outlook of the PERC modules seems promising, as multiple recognized solar brands have already adopted the technology and the expectations around it are huge as well.
With a combination of 15% of Al-BSF and 35% between the HIT and IBC, it is expected that by 2025 the PV market share of PERC cells will be over 50%!
That’s why we keep an eye on them and you should as well!.
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Photo credit: Depositphotos