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PERC Solar Panel:  Strengths, How It Works, vs. Other Panel Techs

The quest for higher panel efficiency in the solar industry knows no bounds and never stops. The PERC solar panel is a relatively new technology in this field, which was first developed in the 1980s. However, its commercial application has only taken off in the past decade due to a combination of surging demand for higher-efficiency panels and remarkable improvements.

This guide will guide you through the various topics related to this panel technology, including:

  • Composition and structure
  • How this technology works
  • Efficiency breakthroughs
  • Comparison with other high-efficiency panel techs
  • PERC panel innovations

What Is the PERC Solar Panel? How Does It Work?

PERC, which stands for Passivated Emitter and Rear Contact, is a type of solar panel technology designed to enhance the efficiency of traditional silicon panels.

Composition and Structure

Instead of being made from entirely new materials, PERC solar panels are essentially enhanced versions of conventional crystalline silicon (c-Si) panels, featuring an additional passivation layer on the rear side along with ingenious optimization.

In general, most layers in a PERC solar cell are identical to those found in conventional silicon cells, with the addition of PERC-specific enhancements. (refer to the figure below the list)

  • Front Contact
  • Anti-Reflective Coating (ARC)
  • Front Passivation Layer: Most modern c-Si panels will be equipped with this layer to reduce surface passivation.
  • Absorption Layer: The n-type and p-type silicon layers collectively form the absorption layer, where light absorption occurs, and electron-hole pairs are generated and separated to produce electricity.
  • Rear Passivation Layer: It is the core feature of PERC cells composed of aluminum oxide (Al₂O₃) or silicon dioxide (SiO₂), responsible for reflecting unabsorbed light back into the cell while reducing recombination.
  • Dielectric Capping Layer: Typically made from silicon nitride (SiNx), it is an enhanced layer designed to insulate the cell and boost durability and passivation quality.
  • Local Back Surface Fields: They are complementary parts of the two previously mentioned layers in PERC cells created by opening small contact points in the rear passivation layer, followed by introducing heavy p-type dopants in these localized regions. They are designed to offer enhanced, localized passivation, minimizing recombination specifically at the points.
  • Rear Contact
Structure of PERC Solar Panel
Schematic drawing of the PERC silicon solar cell
Hannebauer H. Single Print Metal Stencils for High-efficiency PERC Solar Cells. Energy Procedia. 2016;98:40-45. doi:10.1016/j.egypro.2016.10.079

How a PERC Panel Works

As a whole, the working principle of PERC panels involves several key elements.

Firstly, incident sunlight strikes the front surface of the panel. The ARC manages to let the maximum amount of sunlight enter the cell. 

The sunlight then arrives at the front passivation layer where the layer helps to reduce initial surface recombination, allowing for more efficient electron-hole pair generation.

Right after, the photons absorbed by the silicon material generate electron-hole pairs, which are then separated by the electric field within the solar cell, creating an electric potential difference and driving an electric current.

Meanwhile, the passivated rear surface further helps minimize carrier recombination, allowing more carriers to contribute to the electrical current. It also reflects unabsorbed light back into the cell for a second absorption-conversion attempt.

PERC Solar Panels vs. Other Panel Technologies

By putting this technology side by side with others, we can identify the ideal scenarios for the adoption of PERC panels and maximize their benefits.

PERC vs. PERT Panels

First is a comparison between PERC and PERT panels as their names are so close.

Both panel technologies were developed around the same time period, sharing similarities in their design concept.

PERT (Passivated Emitter Rear Totally Diffused) cells also employ a passivation technique to improve cell performance. However, these cells feature a rear surface that is both passivated and diffused, which further enhances light trapping and absorption, leading to even higher efficiency than PERC panels.

On the other hand, PERT technology is largely implemented on n-type c-Si cells. By unlocking the full potential of n-type cells, PERT panels generally have lower LID than PERC panels. This characteristic helps to improve the long-term performance and reliability of these panels.

One key drawback of PERT panels is that they entail a more intricate manufacturing process, which consequently drives up their costs relative to those of PERC products.

PERC vs. IBC Panels

While the PERC technology aims to minimize recombination and facilitate the absorption of secondary light, IBC (Interdigitated Back Contact) panel technology adopts an alternative approach to achieve higher energy yield.

This technology relocates all electrical contacts to the back of the cell, thereby eliminating shading losses that are caused by front-side busbars. As a result, it maximizes the surface area available for energy conversion, optimizing the panel's efficiency.

And thanks for the absence of front-side busbars, IBC solar panels have a sleek, all-black appearance that is more aesthetically pleasing, especially for residential rooftops. Therefore, this panel technology can be a remarkable alternative to genuine BIPV products.

However, IBC panels are generally more expensive than PERC panels due to their complex manufacturing process and advanced circuit design.

PERC vs. Bifacial Panels

By adding a reflective layer on the back, PERC solar panels achieve a certain degree of ‘bifaciality’. By comparison, bifacial panels boast authentic bifaciality.

These panels employ a dual-sided configuration, featuring either tempered, anti-reflective glass on both the front and rear faces, or a glass on the front and a transparent polymer on the rear side. This design enables them to capture additional energy from reflected and diffuse light, thereby enhancing their overall efficiency.

Though the efficiency of bifacial panels is capable of hitting over 25%, it largely depends on the albedo (reflectivity) of the surface below the panels. To maximize their exposure to reflected and diffuse light, they are typically deployed in ground-mount, carport or canopy solar projects.

PERC vs. HJT Panels

Unlike the technologies discussed above, HJT (Heterojunction) panels introduce the most significant alterations to conventional c-Si panels.

The HJT cell consists of a mono c-Si wafer for light absorption, sandwiched by ultra-thin intrinsic amorphous silicon (a-Si) layers for passivation. Then these a-Si layers are topped by doped a-Si layers to form the p-n junction. Generally, TCO layers are also applied to help reduce surface reflection and act as a conductor for the electrons and holes generated.

By introducing a-Si materials into traditional c-Si wafers, HJT panels can achieve higher efficiency than PERC panels with a low temperature coefficient and a low degradation rate.

However, the manufacturing process for HJT panels is more complex and requires significant investment in new equipment and processes. Consequently, this leads to a noticeably higher cost in comparison to PERC panels.

Moving Forward: PERC Panel Innovations

It is the straightforward design of the PERC technology that makes it versatile and adaptive to other types of solar panels.

Though this technology has been predominantly used in mono c-Si panels, it can absolutely be applied in poly c-Si panels as well.

One area where PERC technology has effectively got extended is in the development of bifacial PERC panels. This integration further elevates the utilization of scattered and reflected light in conventional bifacial products, employing a cost-effective approach.

Beyond this, continuous research is underway to explore the application of PERC technology on thin-film panels, such as CdTe and CIGS, to boost their efficiency.

Moreover, there have been studies exploring the integration of PERC panel technology with other advanced cell designs, such as perovskite-silicon tandem cells. These studies aim to optimize the performance of panels by combining the benefits of different technologies. (Messmer et al., 2022)

PERC Solar Panel In-Depth Guide

Pros and Cons of PERC Solar Panels

Until now, the advantages of PERC solar panels have been abundantly clear. Yet, it would be remiss not to mention a couple of their potential drawbacks.

Pros of PERC Solar Panels

  • Several points more efficient than traditional c-Si solar panels 
  • Better performance in low-light and high-heat temperature due to sufficient utilization of light and their enhanced design
  • A cost-effective technology that many can afford attributed to a relatively simply design that can be integrated into existing manufacturing processes with minimal retooling
  • A flexible technology that can be used in various applications ranging from residential and commercial rooftops to large-scale solar farms
  • A versatile technology that can be combined with other technologies like bifacial to further enhance efficiency and performance

The Cons

  • PERC panels tend to have a higher upfront cost than traditional c-Si panels. But their increased efficiency can lead to better long-term savings and a faster ROI.
  • These panels could be more susceptible to LID as a result of the interaction between boron and oxygen within the p-type material, exacerbated by the additional materials and manufacturing steps involved in PERC technology. However, newer manufacturing techniques continue to reduce its impact.

More About the Cost of PERC Panels

Currently, solar panel prices are hovering all-time lows, a situation partly driven by excess inventory held by distributors and manufacturers.

A June news report this year from PV Magazine reveals that mono PERC module prices were assessed at $0.090 per watt, falling into the "low-cost" price bracket at that time. However, foreseeable production cuts, and potential policy changes could stabilize prices in the future.

Are PERC Panels Worth It?

Although PERC solar modules carry a higher price tag than conventional crystalline silicon panels, they often surpass other advanced technologies in cost-effectiveness.

As the technology matures, their price is expected to be overall more friendly, despite fluctuations in market supply and demand.

For many residential, commercial and even large-scale installations, the balance of cost and performance provided by PERC panels often makes them the go-to choice. 

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