Imagine packing a suitcase. To fit more in, you squeeze everything together, overlapping clothes to eliminate wasted space. In theory, this maximizes what you can carry. But what if that aggressive overlap crushes something fragile, making the extra space worthless?
This is precisely the dilemma facing solar engineers working with shingled module technology. By „shingling“—overlapping solar cells like roof tiles—manufacturers can pack more power-generating silicon into the same module area. It’s a brilliant way to boost power density.
But there’s a catch. Overlap too much, and you risk creating problems that silently steal the very power you’re trying to gain. The question is, where is the sweet spot? To find out, our process engineering team at PVTestLab ran a hands-on experiment to define the precise manufacturing window for peak performance. The results might surprise you.
The Shingling Paradox: More Active Area vs. Hidden Losses
First, a quick recap of why shingling is so effective. Traditional solar modules connect cells using metal ribbons that run across the front, casting small shadows and creating electrical resistance. Shingled designs eliminate these ribbons by directly bonding the cells with an electrically conductive adhesive (ECA).
This clever design offers two main advantages:
- More Active Area: No front-side ribbons means more of the cell’s surface is exposed to sunlight.
- Higher Cell Density: Overlapping the cells allows manufacturers to fit more of them into a standard module frame, increasing the total power output.
But this is where the paradox comes in. As you increase the overlap, you introduce two competing loss factors:
- Shading Loss: The edge of the top cell casts a micro-shadow on the one beneath it. A wider overlap creates a wider shadow, deactivating a larger strip of the silicon below.
- Series Resistance Loss: Electrical current must travel through the cell-to-cell bond. A very narrow bond (smaller overlap) can increase resistance, causing energy loss as heat, while a wider bond can alter the current path, also impacting efficiency.
The challenge is that these factors pull in opposite directions. You need enough overlap to create a strong, low-resistance bond, but not so much that shading losses cancel out your gains.
This balancing act isn’t just theoretical; it has a direct, measurable impact on a module’s final power rating (Pmax) and profitability. Operating without knowing your optimal process window is like navigating without a map.
The Experiment: Hunting for the Optimal Overlap
To quantify this trade-off, we put it to the test. Our goal was to pinpoint the exact overlap distance that would deliver maximum power output.
Using our full-scale R&D production line, we manufactured a series of identical mini-modules, varying only one key variable: the cell overlap distance. We created modules with four distinct configurations: 0.8 mm, 1.0 mm, 1.2 mm, and 1.5 mm.
By keeping all other parameters constant—from the cells to the encapsulants and lamination cycle—we could isolate the precise effect of the overlap on module performance. This level of control is fundamental to effective Prototyping & Module Development, ensuring the data reflects the variable being tested rather than random process fluctuations.
Reading the Results: What the IV Curves Revealed
After fabrication, we measured each module’s performance using our AAA Class flasher. Our primary tool for this analysis is the I-V (Current-Voltage) curve, which acts like a fingerprint for a module’s electrical output.
Here’s what the curves revealed:
- The modules with 1.0 mm and 1.2 mm overlaps yielded the healthiest curves, maintaining a high short-circuit current (Isc) and a strong fill factor (the curve’s „squareness,“ which indicates efficiency).
- The 0.8 mm module exhibited signs of slightly higher series resistance, which can subtly reduce the fill factor.
- The 1.5 mm module produced a noticeably lower short-circuit current—the smoking gun for shading loss. Compared to the 1.2 mm version, that extra 0.3 mm of overlap shaded enough of the underlying cells to measurably cut the total current.
The Final Verdict: Power Output vs. Overlap
While I-V curves are great for diagnostics, the number that truly matters is maximum power output (Pmax). When we plotted Pmax against overlap distance, the winner was undeniable.
The 1.2 mm overlap delivered the highest power.
This was the „aha moment.“ Increasing the overlap to 1.5 mm or decreasing it to 0.8 mm both resulted in a power loss. The data beautifully illustrates the trade-off in action.
- Below 1.2 mm: The gains from reduced shading weren’t enough to overcome subtle losses from series resistance and slightly lower cell density.
- Above 1.2 mm: Losses from cell shading became so significant they wiped out any benefits gained from packing the cells more tightly.
Defining the Process Window: Why This Matters for Mass Production
This experiment does more than identify a single „best“ number. It defines a process window—the acceptable range of parameters within which manufacturing can operate to still produce a high-performance, reliable product.
Based on our results, the optimal process window for this specific cell and material combination centers on 1.0 mm to 1.2 mm. If a factory’s stringer machine drifts and starts producing 1.5 mm overlaps, that manufacturer is leaving money on the table with every module coming off the line.
This is where rigorous Process Optimization & Training becomes essential. Understanding your process window allows you to:
- Set Realistic Tolerances: Program machinery with precise targets and acceptable deviation limits.
- Improve Yield: Minimize underperforming modules by ensuring process consistency.
- Diagnose Problems: When module power drops, engineers know to check for deviations in critical parameters like overlap.
- Evaluate New Materials: A different conductive adhesive or cell coating could shift the optimal window, requiring new validation. This is a key part of our Material Testing & Lamination Trials.
Frequently Asked Questions (FAQ)
What is a shingled solar module?
A shingled solar module is a design where solar cells are sliced into strips and overlapped, similar to roof shingles. They are connected using an electrically conductive adhesive (ECA), which eliminates the metal ribbons seen on conventional modules. This design increases the active solar-collecting area and boosts overall power density.
What is series resistance in a solar cell?
Series resistance is the internal resistance within a solar cell and module that obstructs the flow of current. This causes a loss of energy as heat. In shingled modules, the resistance of the cell body, the metal contacts, and the conductive adhesive bond all contribute to the total series resistance.
Why does shading one part of a cell reduce its output?
A solar cell works like a single unit. When one part of it is shaded, that area can’t generate current. Worse, it acts as a resistor, impeding current from the illuminated portions of the cell and others in the string. This effect can significantly reduce the module’s overall power output.
What is an I-V curve?
An I-V (Current-Voltage) curve is a graphical representation of a solar module’s electrical performance. It plots the amount of current a module produces at different voltage levels, from a short circuit (zero voltage) to an open circuit (zero current). The point on the curve where the product of voltage and current peaks is the Maximum Power Point (Pmax).
How does PVTestLab ensure accurate results in experiments like this?
We achieve accuracy through three core principles:
- Controlled Environment: Our entire facility is climate-controlled to ensure that temperature and humidity don’t influence the results.
- Industrial-Grade Equipment: We use the same full-scale production machinery found in major factories, ensuring our results are relevant to the real world.
- Systematic Process: We change only one variable at a time and follow rigorous testing protocols, from material handling to final flash testing, to ensure the data is reliable and repeatable.
Your Path from Theory to Production
The quest for higher solar module efficiency is won and lost in the details. A fraction of a millimeter in cell overlap, a few degrees in lamination temperature, or the choice of one encapsulant over another can mean the difference between a market-leading product and an average one.
Understanding these critical relationships requires more than theory—it demands hands-on, empirical testing in a controlled, industrial environment. By building, measuring, and analyzing, you can replace assumptions with data and turn innovative concepts into reliable, high-performance products.
If you’re developing a new module design or evaluating new materials, the next step is to move beyond the datasheet and see how they perform in reality. Discover how structured prototyping and process validation can accelerate your journey from lab to market.