Half-Cut Solar Panels: Why Halve the Cells? Benefits & Comparisons

When sourcing efficient solar panels on the market, you will usually come across one kind of panel that comprises rectangular cells interconnected instead of cells in traditional square form. This is the half-cut solar panel.

In this article, we will take a closer look at this kind of panel with topics including why to halve the cells, advantages, comparisons with other tech, technological malleability and more.

What Is a Half-Cut Solar Panel?

According to public sources, the half-cut solar panel technology was pioneered by REC Solar in 2014, the same year when the TOPCon technology was released.

Materials, Components and Structure

Half-cut solar panels use the same basic materials as traditional crystalline silicon (c-Si) panels. They are composed of several similar layers that work together for energy conversion. Below is a quick breakdown of the layers found in a typical half-cut c-Si panel:

• Front Cover
• Front Contact
• Anti-Reflective Coating (ARC)
• Encapsulation: Typically made of EVA, it serves multiple vital functions such as mechanical and environmental protection, and optical performance enhancement.
• Absorption/Photovoltaic Layer: This core layer is made up of base and emitter. The former can be n-type or p-type silicon, while the latter is doped with a particular element(s) to create a p-n junction, depending on the electrical property of the base.
• Encapsulation
• Back Contact
• Backsheet
• Frame
• BSF (Optional)

It's evident that basically there are no distinctions regarding materials and layer positioning between half-cut and traditional c-Si panels.

What set half-cut panels apart are several unique aspects:

• Each traditional square cell is cut into halves, which translates to double the number of cells within a panel. For example, a traditional panel configured with 72 cells will become a 144-cell panel.
• Half-cut cells within the panel utilize both series and parallel wiring. The panel is generally divided into two separated sections, each functioning independently. Cells within each section are connected in series and then the two sections are connected in parallel.
• Bypass diodes are usually integrated across groups of cells in a half-cut panel, allowing for better performance management.

Why Halve the Cells?

While there are several notable features, the core is the halving of the cell size. This approach serves two primary purposes.

• Reduced Resistive Losses: Halving the cells decreases the current in each cell. As per Joule's Law, this reduction in current can decrease the electrical resistance losses, potentially contributing to higher overall efficiency and production.
• Improved Shade Tolerance: The shading effect is an issue that nearly all solar systems will suffer. By leveraging the benefits of half-cut cells and structured wiring, half-cut solar panels exhibit improved resilience to shading variations, minimizing performance losses in shaded conditions.

How a Half-Cut Panel Works?

The general workflow of half-cut panels is on par with that of other panel products. That being said, their unique design and configuration have a couple of notable implications:

• If all cells are at an ideal state. Each half-cut cell generates roughly half the current as compared to a full-sized cell, reducing resistive losses. Within a separated section, the overall current remains the same while the voltage adds up proportional to the cell number. Combined in parallel, the voltage of the two sections persists while the current doubles to meet desired output.
• When a portion of cells or one substring is malfunctional or shaded, the substring will be isolated by the bypass diode while the other(s) can remain operational. The reduced cell size and increased substring number help to minimize the impact of shading effect and maintain optimal panel performance.

What Are the Advantages & Disadvantages of Half-Cut Modules?

To summarize, what benefits can you expect from half-cut solar modules, and what potential drawbacks should you consider when making your decision?

The Advantages of Half-Cut Panels

Primarily, the two primary purposes of halving the cells as discussed earlier—reducing resistive losses and improving shade tolerance—yield a direct increase in efficiency and power output compared to traditional full-sized cell panels. Some studies report a power gain of approximately 5% when adopting half-cut cell technology.

Beyond the essential benefits above, half-cut panels can also provide several marked advantages as follows:

• Reduced Hot Spots for Enhanced Longevity: As half-cut cells generate lower current, not only less resulting energy in the form of heat is produced, but also heat dissipation capability of the panel is enhanced. Consequently, the risk of severe hot spots is minimized and the panel is less prone to degradation and damage from hot spots. 
• Improved Durability: The smaller size of the cells in half-cut panels makes them less sensitive to micro-cracks and other physical/mechanical damage, which improves their reliability in harsh operating conditions.
• More Aesthetically Appealing: The layout of half-cut cells generally gives the panels a more uniform and aesthetically pleasing appearance, which can be attractive for installations where aesthetics is highlighted.

Their Downsides…

• Increased Risk of Defects: There is a higher probability of bad contacts or defects in the half-cut cells since the design results in roughly twice the number of soldered connections. This requires stringent manufacturing techniques and quality control to ensure reliability. However, it is reassuring that with the aid of modern precise laser cutting and soldering technologies, the risk is largely mitigated.
• Higher Costs: The production of half-cut panels involves more manufacturing processes. This leads to a higher cost of production than that of traditional panels. But their improved efficiency and output make them a valuable investment, offering long-term cost savings.

Comparing Half-Cut Panels With Other Advanced Panels

Half-cut cell panels feature several striking benefits. How do they stack up against other advanced panels? A brief comparison will help you develop a better grasp of this technology.

Half-Cut Panels vs. PERC Panels

PERC modules are also aimed to yield higher efficiency and production, but implement a different approach.

These panels add a rear passivation layer to the back of the panel. This layer is typically composed of Al₂O₃ or SiO₂, and was tasked with reflecting unabsorbed light back and reducing recombination. Apart from this, a dielectric capping layer is generally combined to enhance the quality of passivation. 

That is to say, the approach of PERC panels is more inclined towards the micro level of photovoltaics. In comparison, half-cut cell panels are more focused on the optimization of the electrical aspect to reduce losses and improve results.

Half-Cut Panels vs. Shingled Panels

Shingled solar panels also underscore the advantage of reduced cell size. 

However, while half-cut panels halve the cells, shingled panels slice a traditional cell into more small pieces/strips which causes even smaller cells and lower resistive losses.

Another marked difference is that the small cells of shingled panels are overlapped together like shingle materials on rooftops. This innovative connection method shrinks the gaps between cells and in turn boost the active area for light absorption and conversion, which is conceptually similar to IBC panels.

On the other hand, the revised layout makes half-cut panels more appealing than traditional panels. Shingled panels take it to the next level with an even more uniform and aesthetically pleasing appearance.

However, shingled panels also have a higher cost and the adhesive used to bond the cells can potentially degrade over time. Hence, cooperating with reputable manufacturers is important.

Can Half-Cut Cell Technology Be Combined With Other Techs?

Yes, half-cut cell technology is flexible and can indeed be combined with other advanced technologies to further enhance the performance, efficiency and reliability of solar panels.

This technology is often used with PERC technology, which offers higher efficiency and production by reducing resistive losses and recombination.

Moreover, some pioneer manufacturers have tried to combine half-cut with IBC and bifacial technologies. These combinations can give rise to higher-performing modules by leveraging the strengths of each technology.

For example, bifacial technology can enable the module to capture light from both sides of the panel, increasing energy generation.

Glancing at Recent Advancements in Half-Cut Technology

Half-cut solar panel technology continues to evolve rapidly.

In addition to ongoing research and improvements on combinations with other cutting-edge techs, recent advancements include the integration of heterojunction technology, which combines silicon in different forms to maximize efficiency. For instance, REC’s Alpha Pro M Series line utilizes 120 heterojunction half-cut cells and can achieve efficiencies of up to 22.5%.

Furthermore, the industry also strives to establish an accurate modeling framework to evaluate the performance of half-cut solar technology. The framework is necessary to study and detail how half-cut modules respond to shading conditions and it is crucial to improve the technology, develop new MPPT algorithms and evaluate the performance of photovoltaic systems.

Wrapping Up

Half-cut technology is becoming increasingly popular in residential as well as C&I applications. With its superior technological malleability and as manufacturing processes continue to improve, the cost-effectiveness and prevalence of this technology are expected to increase.