As solar energy systems continue to grow in scale and sophistication, homeowners, commercial operators, and utility‑scale developers share a common priority: keeping solar modules performing at their highest possible output for as long as possible. Two phenomena—Light‑Induced Degradation (LID) and Potential‑Induced Degradation (PID)—can silently chip away at that production if not properly understood and managed. Both issues originate from physical and electrical stress within photovoltaic (PV) modules, but they appear in different ways and require distinct strategies to mitigate.

A solid grasp of how LID and PID occur, why they matter, and what can be done about them can help system owners protect their investment and maintain healthy energy yields throughout the system’s lifetime.

Understanding Light‑Induced Degradation (LID)

LID refers to the initial drop in power output that occurs when crystalline silicon solar cells are exposed to sunlight for the first time. It might sound counterintuitive—light is what enables the panel to produce power, after all—but this early decrease is tied to the material properties of silicon itself.

Most modern crystalline silicon cells contain a small amount of boron, added intentionally during manufacturing to create the p‑type semiconductor layer. When these boron‑doped cells encounter sunlight for the first time, a reaction occurs between boron and oxygen within the silicon lattice. This interaction leads to defects that temporarily reduce the cell’s ability to convert sunlight into electricity.

This drop tends to happen quickly. Many modules experience most of their LID within the first few hours to days of exposure. The typical impact ranges from 1% to 3%, though certain cell types may see slightly more or less. While this might not sound dramatic, even small percentages translate to meaningful long‑term losses when accumulated across decades.

Variations in LID Based on Cell Technology

Different photovoltaic technologies experience LID differently:

Standard boron‑doped p‑type cells: These are the most susceptible, as the classic boron‑oxygen defect is directly tied to their cell chemistry.

Gallium‑doped p‑type cells: Gallium has largely replaced boron in many premium modules because it does not form the same defect with oxygen. Gallium‑doped cells demonstrate little to no LID.

N‑type cells: Because they reverse the doping structure and avoid boron in the base layer, they are virtually immune to LID.

Heterojunction and TOPCon cells: These advanced structures generally exhibit minimal LID due to improvements in wafer quality and passivation layers.

As the solar industry continues refining wafer manufacturing and doping techniques, LID has become less pronounced, though it still remains relevant for many module types and in certain production batches.

Managing and Minimizing LID

Manufacturers have responded to the LID challenge through multiple strategies:

Pre‑light soaking: Some module factories expose panels to intense light before shipping, stabilizing the modules before installation.

Improved wafer quality: Reducing oxygen content during the silicon ingot growth process dampens the boron‑oxygen interaction.

Alternative doping materials: As mentioned, gallium and other dopants reduce susceptibility to LID significantly.

System owners generally cannot influence LID once panels are installed, so the main opportunity lies in selecting hardware with low‑LID cell technologies. Looking for modules with gallium doping or n‑type architecture is an effective way to ensure minimal early‑stage degradation.

What Is Potential‑Induced Degradation (PID)?

PID is a different phenomenon altogether. Instead of light triggering chemical defects, PID stems from electrical stress within the module. When the voltage potential between a solar cell and the module frame becomes too high, unwanted currents can flow across insulating materials. Over time, this leakage current causes charge accumulation, ion migration, and deterioration of the cell’s ability to generate power.

Unlike LID—which happens early and stabilizes—PID can progress slowly and steadily over years. If not addressed, PID can reduce module output by double‑digit percentages and may continue getting worse unless the cause is removed.

PID tends to be most prominent in high‑voltage systems, such as large commercial rooftop arrays and utility‑scale plants. However, any environment that combines high system voltage, heat, and humidity increases the risk.

Why PID Happens

PID typically results from one or more of the following:

Module grounding configuration: If the negative pole of the array is grounded, certain modules can experience a large negative potential relative to their frame, driving leakage currents.

Inadequate encapsulation or insulation: Imperfections or aging in EVA (encapsulant), backsheet materials, or glass coating allow ions to move more easily.

System voltage stress: Systems operating at 1000V or 1500V can be more susceptible, especially in warm, humid climates.

High humidity and temperature: These environmental factors accelerate ion migration within the module.

The signature of PID is consistent: a slow loss of power that becomes more pronounced over time, often appearing unevenly across a string or array. Electroluminescence imaging can reveal characteristic dark areas that indicate where PID has taken hold.

Reducing the Risk of PID

PID is preventable with thoughtful equipment selection and system design:

PID‑resistant modules

Manufacturers now offer modules with improved encapsulants, better cell passivation, and enhanced insulation layers. These are engineered specifically to block ion migration even under high‑voltage stress.

PID‑resistant inverters

Many inverters include anti‑PID functions that apply small reverse voltages at night, effectively neutralizing the charge buildup that drives PID.

Optimized grounding strategies

Carefully planned grounding and array configuration can minimize large potential differences between cells and module frames.

Environment‑aware installation choices

In regions with high humidity or strong temperature swings, using PID‑resistant components is especially prudent.

Regular monitoring

Early detection is key. If production data or imaging suggests PID may be beginning, system owners can often slow or reverse the trend by adjusting grounding or activating inverter anti‑PID modes.

How LID and PID Affect Long‑Term Performance

While both LID and PID reduce output, their impacts differ in timing and progression:

LID is front‑loaded and stabilizes quickly. Most of the degradation happens in the first hours or days.

PID is progressive and can worsen over months or years if not addressed.

LID is generally predictable. PID is more variable and depends heavily on system design, installation quality, environment, and material choices.

For system owners, the concern is cumulative impact. A small LID effect combined with an unmanaged PID issue can create compounding losses. Fortunately, the tools and technologies to reduce both problems are stronger now than ever.

The Importance of Material Quality and Manufacturing Standards

High‑quality modules go a long way in preventing both LID and PID. Manufacturers increasingly rely on advanced wafer production, robust passivation layers, improved encapsulants, and low‑defect cell structures. These innovations help cells maintain stable electrical characteristics throughout their lifespan.

Certifications and testing procedures now routinely include LID and PID stress tests. When evaluating modules, reviewing these certifications can give confidence that the product has undergone accelerated aging procedures and has demonstrated resilience under simulated field conditions.

Working with trusted brands and verified supply chains is equally important. Quality inconsistencies in silicon wafers, EVA layers, or backsheets can magnify susceptibility to PID or influence the intensity of LID.

How Monitoring Helps Detect Problems Early

Modern PV systems benefit from real‑time monitoring and analytics. Subtle deviations in power production can reveal early signs of PID, especially when comparing string‑level or module‑level outputs.

Key indicators worth tracking include:

Differences between strings with identical orientation and irradiance

Gradual performance decline not explained by soiling or shading

Hotspots or dark patterns detected through thermal or electroluminescence imaging

Because monitoring platforms can store historical data, they make it possible to spot trends that might otherwise go unnoticed. The sooner potential PID issues are identified, the better the chances of mitigating long‑term losses.

The Growing Role of N‑Type Technologies

One of the most significant shifts in the solar industry has been the rapid adoption of n‑type cell technologies. These architectures inherently avoid boron‑oxygen defects, leading to natural immunity to LID. At the same time, they often demonstrate enhanced temperature performance and better resistance to PID due to improved passivation and encapsulation layers.

As n‑type modules—such as TOPCon and heterojunction—continue to expand their market share, the risks associated with LID become less pronounced for new installations. Even so, PID resilience still depends on robust system design and proper material selection.

Practical Steps for System Owners and Installers

To maintain the highest possible solar production, it helps to take a proactive approach:

Choose modules tested for both LID and PID resistance.

Favor gallium‑doped or n‑type modules when possible.

Use inverters with anti‑PID functions, especially on high‑voltage arrays.

Follow manufacturer guidelines for grounding and system configuration.

Conduct periodic performance checks and inspections.

Use high‑quality mounting and cabling materials to maintain consistent grounding integrity.

Small design choices during installation can have a long‑lasting influence on system stability and performance.

Building a More Durable Solar Future

LID and PID may sound like technical concerns reserved for manufacturers and engineers, but they influence every solar system’s long‑term productivity. Understanding how these mechanisms work—and selecting equipment built to withstand them—helps ensure that a solar installation delivers consistent, reliable energy throughout its operating life.

By pairing quality components with thoughtful design and periodic monitoring, system owners can safeguard their production and maintain strong returns for years to come.