Introduction

Photovoltaic modules are the heart of every solar power system – they convert sunlight into electricity. Their performance largely depends on the condition of the solar cells inside. However, many types of damage remain invisible until energy yields drop. This is where electroluminescence in photovoltaics comes into play: an imaging method that makes microscopic defects visible – quickly, non-destructively, and with precision.

Whether during transport, production, or after a storm: damage such as microcracks in solar modules, cell fractures, or production defects can significantly impair performance. With a professional EL test of solar modules, such weaknesses can be detected before they cause financial or safety-related consequences – a real benefit for operators, installers, manufacturers, and insurers alike.

1. What is Electroluminescence in Photovoltaics?

Electroluminescence (EL) is the physical phenomenon where certain materials emit light when electrically stimulated. In photovoltaic quality testing, this effect is used to visualize the internal condition of solar cells.

To do this, a voltage is applied in the opposite direction of the normal operating current. The solar cells then emit a weak light in the near-infrared (NIR) spectrum. This light is invisible to the human eye but can be captured using special infrared cameras.

The result is an electroluminescence image – a kind of “X-ray” of the module:

• Intact cells appear bright and uniform.
• Damaged areas, such as from microcracks or cell fractures, remain dark or show irregular patterns.
• Production defects, such as cell mismatch, hotspots, or faulty solder joints, become visible.

This method is contactless, non-destructive, and delivers quick, clear insights into the quality and functionality of a module – whether brand new, used, or installed for years.

2. Microcracks & Cell Fractures – Causes and Consequences

Microcracks in Solar Modules

Microcracks are tiny fissures within the solar cell. They are usually caused by mechanical stress – for example during transport or by external influences after installation. They locally interrupt the flow of electricity, can create hotspots, and lead to long-term performance losses.

Cell Fractures in Photovoltaics

Cell fractures affect larger areas of the solar cell. Cracks can run across multiple cell sections and disconnect entire strings electrically. This can result in significant yield losses and safety risks – especially under high currents and voltages.

Both types of damage can be reliably and early detected through a solar module EL test.

3. Photovoltaic Quality Testing Before Installation – Detecting Risks Early

Before photovoltaic modules are permanently installed, it pays to closely inspect their condition. Many defects are invisible to the naked eye but may have already occurred during shipping – or even earlier, during production.

Typical damage caused by transport or handling:

• Vibrations and shocks can create microcracks in the cell structure, initially unnoticed but later leading to hotspots or power loss.
• Improper stacking causes localized pressure, which can deform glass and cells – even leading to visible cell fractures.
• Point loads – for example, when using forklifts – often damage individual cells, reducing the module’s overall performance.

Production defects visible with electroluminescence:

• Poor solder joints, which may result in contact failure or hotspots.
• Cell mismatch, where cells of different efficiency levels reduce the module’s overall output.
• Cell defects, such as:
  • Dark cells
  • Chain patterns
  • Finger interruptions
  • Shunts
  • Pressure marks

These cell defects provide clear indications of the sorting and quality of the cells used – and can be easily identified using electroluminescence.

Especially before installation – and before modules are permanently mounted and wired – electroluminescence is an efficient way to ensure quality. As part of an incoming goods inspection, it offers reliable insight into hidden defects and enables a sound decision: install, claim, or reject.

4. Testing Installed Modules – Detecting Damage Early

Even after installation, modules are not immune to damage. Environmental stress and installation errors can lead to structural issues, such as:

• Hail causing localized cell fractures.
• Snow load bending the module surface, increasing the risk of cracks.
• Storms or high wind loads loosening mounting systems or causing module movement.
• Incorrect installation, such as uneven clamping or over-tightened screws, which creates internal stress.
• Thermal cycling, with large temperature differences between day and night, leading to microcracks over time.

The EL test of installed solar modules makes these issues visible – even when they are not externally noticeable. This is particularly valuable for performance losses, insurance claims, routine maintenance, or inspections before warranty expiration.

5. The SecondSol Test Center – Solar Module Testing with State-of-the-Art Technology

At the SecondSol Test Center, EL testing of solar modules is performed using state-of-the-art equipment – including the advanced MBJ Flasher. This enables both precise electroluminescence images and exact power measurements under controlled conditions.

SecondSol provides professional services for:

• Installers who want to evaluate modules before installation,
• Operators suspecting yield losses,
• Insurers requiring objective condition assessments,
• Dealers and manufacturers who value transparency and quality assurance.

From incoming goods inspection to fault diagnosis – photovoltaic quality testing at SecondSol ensures reliability across the entire value chain.

Conclusion

Electroluminescence is a proven, highly precise method for detecting damage and production defects in photovoltaic modules. It reveals what remains hidden to the eye – making it an indispensable tool for everyone working with PV modules.

Especially before installation, an EL test of solar modules provides a crucial step in quality assurance. For operators and insurers, it delivers reliable data before financial risks occur – or before a warranty expires.

SecondSol supports this process with a professional test center – equipped with the latest technology and committed to making true quality visible.

Want to test your solar modules and make sure they deliver as promised? The SecondSol Test Center offers reliable electroluminescence testing for operators, installers, dealers, and manufacturers.

Test your solar modules now: