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What you need to know about PERC solar cells

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Conventional silicon photovoltaic (PV) cells have long been the standard in the solar industry. But as the technology matures and approaches hard efficiency limits, researchers and manufacturers have started to embrace a relative newcomer — the Passivated Emitter and Rear Contact (PERC) solar cell.

In this article, we’ll look at the core benefits of PERC solar cells, how they work, how they’re made, and even how to sell them. But first, let’s get into some background about how conventional solar cells work and what limitations they present.

How standard solar cells work

Traditional solar cells contain two layers of silicon, commonly called “n-type” and “p-type” for their negative and positive charge behavior. A solar panel creates electricity when sunlight hits the solar cells, knocking electrons loose from the n-type layer as the p-type layer accepts them.

These flowing electrons are what create an electric field — and by extension — clean solar power for the customer’s home or business.

simplified-silicon-module
A simplified cross-section of a silicon solar cell. Sunlight (orange) hits the solar cell and the light knocks electrons (blue) loose within the silicon material. Electrons that make their way to the electrical contact can then flow through an attached circuit, providing electrical energy.

Although this basic design has served the solar industry well, plain PV cells suffer from several types of efficiency losses, including:

  • Insufficient sunlight capture either due to light reflecting off panel surfaces or because of wires and other components blocking light
  • Excessive heat buildup, especially as light hits the back-most surface of the PV cells
  • Free electrons being knocked out of alignment due to scattered light refraction
  • Electrons recombining with the silicon material on the front and back of the solar cell
solar-cells-efficiency
Within a solar cell, some efficiency is lost when light is not converted to electrons, or the resulting electrons don’t make their way to the rear for contact. Researchers are constantly working to reduce these losses.

Fortunately, some of these efficiency losses can be mitigated with technology. 

For example, adding a front passivation layer can help stop front-side recombination. This strategy also helps to reduce some reflection. To prevent unwanted electrons from moving through the cell and hitting the rear contact, it’s possible to add a back surface field layer or place all the wires on the back of the panel during the manufacturing process.

The hardest efficiency losses to manage, however, are excessive PV panel heating and back-side recombination. Because of these limits, the maximum efficiency of standard solar modules hovers around 20% in the field.

typical-silicon-module
Most silicon modules have layers that help avoid losses; the front layer reduces reflection losses and also prevents electrons from being lost on the front edge. The rear back surface field repels electrons, reducing the number that make it to the rear contact.

What are PERC solar panels and how do they work?

First introduced in 1989, PERC panels are modified silicon cells that have an additional layer on the back. Because this extra layer is reflective, it is able to send unused light back across the n-type and p-type junctions to generate more energy. Better still, this reflective surface also helps to reduce rear recombination and prevent longer wavelengths from becoming heat that would otherwise impair the cell’s performance.

Early commercial implementations of PERC technology ran into trouble — largely due to increased light-induced degradation. But with steady improvements over the years, PERC modules have since achieved solar generation efficiencies up to 12% higher than their traditional silicon counterparts.

As a result, solar PV installers are able to save time and reduce costs when using the newer PERC standard. This is because fewer panels are needed to achieve the same solar power output. Using fewer panels also helps to reduce the amount of racking, wiring, and MLPE devices needed to connect everything together.

For example, even if roof space is not a major concern, it may be possible to save installation time and costs by using higher efficiency PERC modules. If a site takes 40 standard modules or 38 PERC modules to reach the desired annual production, you’re able to reduce the amount of racking, wiring, and MLPE devices needed to connect everything together.

PERC-silicon-module
Like other high-efficiency modules, PERC modules can be used to maximize production on a limited roof area. If you’re installing on small roof areas or buildings that are partially shaded, PERC modules would be a good option.
Different buyers want different things — including different types of panels — click above to get our research-based guide on the 5 types of solar buyers.

PERC module production

PERC solar modules are structurally similar to other silicon panels on the market, which is a distinct advantage for manufacturers.

Even though there are additional costs when creating passivation and rear contact capping layers, panel manufacturers are able to reuse existing production equipment with minimal retooling required.

This places PERC manufacturing costs on par with conventional silicon cell production. Although PERC panels remain slightly more expensive, these costs are largely offset by the increased efficiency gains – which yields higher lifetime utility bill savings and carbon offsets for the end-user. And as the technology continues to mature thanks to economies of scale and R&D, PERC cells will likely continue to benefit from even larger efficiency gains and cost reductions moving forward.  

Types of PERC solar modules

Mono PERC cells

Monocrystalline solar cells are cut from a single piece of silicon, making them more efficient than polycrystalline panels. Additional PERC layers can be added to help further increase efficiency rates.

Poly PERC cells

Unlike uniform monocrystalline cells, polycrystalline PERC cells are manufactured using a blend of silicon shards. This mix yields lower efficiencies, but polycrystalline cells are cheaper to manufacture. 

Just like with monocrystalline cells, adding a PERC layer can significantly increase the efficiency of polycrystalline cells without dramatically increasing their manufacturing costs. But because higher solar power output is the Holy Grail of the industry, the more efficient monocrystalline PERC cell is the preferred standard for most new PV installations.

Click the image to learn more about the advantages of PERC cells, how to model them, and how to sell them in our free, on-demand webinar.

Growth in PERC cell production

Global demand for PERC modules has skyrocketed in recent years. In 2014, for example, total installed PERC capacity accounted for less than. By 2022, that number had mushroomed to nearly 160 GW. That researchers in Germany have also developed a way to manufacture PERC cells from 100% recycled silicon materials suggests that the technology’s dominance will only grow as extant PV systems reach the ends of their useful lifetimes.

How offering PERC solar panels can increase solar sales

The main selling point of PERC panels is their efficiency. Because they make better use of space, fewer modules are required to produce the same solar output as a standard silicon panel. For customers who may have space constraints, offering PERC panels is a compelling option. But even if roof real estate isn’t a factor, it’s possible to save installation time and costs by using PERC modules. 

In effect, PERC technology used to be a competitive advantage. But due to its cost parity and higher efficiencies, it has since become the official industry standard for new solar PV projects. In fact, the International Energy Agency reports that PERC panels currently enjoy almost 75% market share among new PV installations.

Next steps

A knowledgeable customer is one of our best weapons when selling solar. Make sure your customers have all the information by giving them a free Solar Sales Follow Up Kit. It has all the background a customer needs on the basics of solar, and can help set their mind at ease.

Click the image to download The Solar Sales Follow Up Kit.

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