What you need to know about PERC solar cells

Want to learn more about the solar industry? Join us for Empower 2024 on June 5-6! You’ll hear from industry experts on everything from what to expect for the rest of 2024, to how AI is affecting the industry, and more. Register Now Note: This blog was originally published in 2018. It was updated in January, 2024 to reflect the most recent information. If you have any questions, please contact us. 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.

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

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.

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 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 yield 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 industry’s Holy Grail, the more efficient monocrystalline PERC cell is the preferred standard for most new PV installations.

Growth in PERC cell production

Global demand for PERC modules skyrocketed in the late 2010s and continues to see steady growth. In 2021, the PERC solar sales market was estimated at around $150 billion and is projected to hit $290 billion by 2030. While PERC cells are undoubtedly the top panel on the market, some industry experts theorize that PERC cells may be phased out in the next few years, favoring N-type solar cells due to their “superior conversion efficiency.”

Pros and cons of PERC solar panels

There’s a reason PERC cells are the industry standard — they’re highly efficient and a much-improved type of PV technology compared to traditional solar panels. However, compared to the new development of N-type cells, there are some disadvantages. Let’s review the pros and cons of PERC solar panels.

Pros of PERC solar panels

• More efficient compared to conventional silicon solar panels
• Work better in low light and high heat conditions compared to standard solar cells
• Are more affordable than N-type solar panels

Cons of PERC solar panels

• Slightly more expensive compared to conventional silicon panels
• Don’t produce as much power compared to N-type cells
• Are more negatively influenced by high temperatures than N-type cells

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. The same case goes for customers who don’t get as much direct roof sunlight or customers who live in high-heat areas: PERC cells perform better in these conditions compared to traditional cells.  But even if roof real estate or weather conditions aren’t factors, it’s possible to save installation time and costs by using PERC modules. Because PERC cells are more efficient, less panels will need to be installed.

Side-by-side cost comparison: Traditional vs. PERC Solar Panels

Cost will still be a major consideration for many clients. To seal the solar deal, it’s easier to outline how PERC solar panels are a better value in the long run, even if they’re a larger upfront investment. The table below provides a good visual.

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.