Knowledge Center



What is photovoltaics?

Photovoltaics (sometimes referred to as “PV”) combines the Greek prefix “photos” (=light) and the suffix “volt” designating the generation of electrical energy, in recognition of the Italian physicist Alessandro Volta (1745-1827). Photovoltaics describes the capability of an object to convert light into electrical energy. Solar photovoltaics (solar PV) devices convert sun rays into electricity.

What is PERC?

A Passivated Emitter and Rear Cell (PERC) is a type of solar cell that uses a passivating layer on the rear surface of the cell to improve its efficiency. The passivating layer, typically made of a stack of aluminum oxide and silicon nitride, serves to reduce recombination of electrons and holes at the rear surface of the cell, which allows for more efficient collection of the generated electrical current.

PERC cells typically have higher efficiency than traditional solar cells, which can translate into more power output per unit area.

It is worth noting that, a common variation of the PERC cell is the bifacial solar cell, which is a type of solar cell that can absorb light on both front and back side and can increase the overall power output by up to 30%.

Conventional Solar Cell
PERC Solar Cell

What is TOPCON?

Tunnel Oxide Passivated Contact 

What is LID?

Light Induced Degradation. Some solar PV devices may degrade when exposed to sunlight. There are several mechanisms that may be at stake in a module degradation, however, the most commonly associated to “LID” is the formation, under light, of a molecular complex within the silicon crystal involving one atom of Boron and one atom of Oxygen. The so-called “B-O complex” have microscopic properties reducing the efficiency of the device (by creating recombination centers for electrons and holes). 

What is LeTID?

Light and Elevated Temperature Induced Degradation  

What is PID?

Potential Induced Degradation

What are the IAM parameters of a module?

Incident/Incidence Angle Modifier 

What is a typical module open-circuit voltage?


What is a typical module short-circuit current?


What are the temperature coefficients of a solar module?

Temperature coefficients are a measure of how the performance of a solar module changes with temperature. The two most commonly quoted temperature coefficients for solar modules are the temperature coefficient of power (Pmax) and the temperature coefficient of the open-circuit voltage (Voc).

The temperature coefficient of power (Pmax) is a measure of how the maximum power output of a solar module changes with temperature. It is usually expressed as a percentage per degree Celsius. For example, if a solar module has a Pmax temperature coefficient of -0.5%, it means that for every 1°C increase in temperature, the module’s maximum power output will decrease by 0.5%.

The temperature coefficient of the open-circuit voltage (Voc) is a measure of how the open-circuit voltage of a solar module changes with temperature. It is also usually expressed as a percentage per degree Celsius. For example, if a solar module has a Voc temperature coefficient of -0.3%, it means that for every 1°C increase in temperature, the module’s open-circuit voltage will decrease by 0.3%.

It is important to note that temperature coefficients can vary depending on the type of solar cell technology and the manufacturer, so it is important to consult the specific data sheet of a solar module to understand its exact temperature coefficients.

What are the 2 main module product certificates?

IEC 61215 and UL 61215 are international and national standards for the design qualification and type approval of crystalline silicon terrestrial photovoltaic (PV) modules, and IEC 61730 and UL 61730 are the international and national standards for the safety qualification and testing of PV modules.

The IEC 61215 and UL 61215 standards cover the design qualification and type approval of PV modules, including requirements for mechanical, electrical, and environmental performance testing. This includes tests for maximum power output, power output under different lighting conditions, and performance under various environmental conditions such as temperature, humidity, and wind. The standard also includes guidelines for the design and construction of the module, including the use of appropriate materials and the proper integration of electrical and mechanical components.

The IEC 61730 and UL 61730 standards cover the safety qualification and testing of PV modules. These standards include requirements for electrical safety testing, including testing for overvoltage and short-circuit conditions, as well as tests for the module’s ability to withstand various environmental conditions, such as high winds and hail. The standard also includes guidelines for the safe installation and maintenance of PV modules.

Both standards are widely recognized and adopted around the world, and PV modules that are certified to meet these standards are considered to be of high quality and safe for use in residential and commercial applications. Manufacturers of PV modules will typically have their products tested and certified to these standards in order to demonstrate their compliance and to be able to sell their products in different markets.

What is the best tool to identify cell cracks in c-Si technology in the field?

Electroluminescence (EL) 

What are the 3 main segments in the PV market?

There are a few key differences between the residential, commercial and industrial, utility-scale, and community-solar segments of the solar power industry.

Residential: Residential solar systems are designed for use in single-family homes and small multi-family buildings. These systems are typically smaller in size, with a capacity of less than 10 kilowatts (kW), and are designed to meet the energy needs of the individual household or building. They are typically owned and operated by the homeowner or building owner.

Commercial and Industrial: Commercial and industrial solar systems are designed for use in larger buildings and facilities, such as office buildings, warehouses, and manufacturing plants. These systems are typically larger in size, with a capacity of 10 kW to several megawatts (MW), and are designed to meet the energy needs of the facility or business. They can be owned and operated by the facility or business owner or by a third party through a power purchase agreement.

Utility-Scale: Utility-scale solar systems are large-scale systems, typically with a capacity of several MW or more, that are designed to generate electricity for sale to utilities and other large energy consumers. These systems are typically owned and operated by utility companies, independent power producers, or other large energy companies.

All these segments have different characteristics in terms of system size, ownership, and customer base, but they all share the goal of providing clean and sustainable energy to power homes, businesses and communities.

What is “community solar”?

Community solar, also known as shared solar, refers to solar systems that are owned by a community or a group of investors and that provide electricity to multiple customers or properties. This allows customers who cannot or choose not to install solar on their own property to still access the benefits of solar power. Community-solar projects can be either utility-scale or residential-scale, and they can be connected to the grid to provide power to multiple customers, or they can be off-grid to provide power to a specific community.

What is the “Balance-Of-System”?

The “Balance-of-System” (BoS) refers to all of the components and equipment in a solar power system that are not the solar panels themselves. This includes the inverter(s), wiring, mounting hardware, and other electrical and mechanical components necessary to connect the solar panels to the electrical grid or to a battery storage system.

Some of the key components of the BoS include:
Inverter: The inverter converts the direct current (DC) electricity produced by the solar panels into alternating current (AC) electricity that can be used by the building or fed into the electrical grid.

Mounting hardware: This includes the racking, brackets, and other hardware used to securely mount the solar panels to the roof or other structure.

Wiring and electrical components: This includes the cables, conduit, and other electrical components used to connect the solar panels to the inverter and to the electrical grid or battery storage system.

Grounding and lightning protection: This includes the components and equipment necessary to properly ground the solar power system and protect it from lightning strikes.

Monitoring and control equipment: This includes equipment and software used to monitor the performance of the solar power system, including the solar panels, inverter, and other components, as well as to control the system’s operations.

Overall, the BoS includes all the components that are necessary to connect the solar panels to the electrical grid or battery storage system, and to ensure that the system is safe, reliable, and operates at peak performance.

What are the differences between a central inverter and a string inverter?

A central inverter and a string inverter are two different types of inverters used in solar power systems.

Central inverter: A central inverter is a large, centralized inverter that is responsible for converting the direct current (DC) electricity produced by all of the solar panels in a solar power system into alternating current (AC) electricity. The central inverter is typically located in a utility room or other central location and is connected to the solar panels through a network of DC cables.

String inverter: A string inverter, also known as a microinverter, is a small inverter that is connected to one or more solar panels. The DC electricity produced by each individual panel is converted to AC electricity by its own string inverter, instead of all the panels being connected to a central inverter. The string inverters are typically mounted on the back of the solar panel or nearby and are connected to the solar panels through a network of DC cables.

The main difference between a central inverter and a string inverter is the way they are connected to the solar panels. A central inverter is connected to all the solar panels in a system, while a string inverter is connected to each individual panel or group of panels.

Central inverters are typically more efficient and have a higher power capacity than string inverters, but string inverters have the advantage of being more flexible, as they can be used in a variety of different solar panel configurations. Additionally, string inverters are more reliable and less affected by shading or partial shading, as each panel has its own inverter, which means that a shading issue on one panel won’t affect the performance of the whole system.

What are the differences between LFP (Lithium Iron Phosphate) and NMC (Nickel Magnesium Cadmium) Li-ion batteries?

Lithium Iron Phosphate (LiFePO4 or LFP) and Nickel Manganese Cobalt Oxide (NMC) are two common types of Lithium-ion batteries.

The main difference between the two is in their chemistry. LFP batteries use lithium iron phosphate as the cathode material while NMC batteries use a combination of nickel, manganese, and cobalt. This leads to some key differences in their performance:

LFP batteries have a lower energy density compared to NMC batteries. They typically store less energy in the same size and weight.

LFP batteries have a longer cycle life than NMC batteries. They can be charged and discharged more times before losing capacity.

LFP batteries have better thermal stability and are less prone to catching fire or exploding.

LFP batteries have a lower peak power output compared to NMC batteries. They can’t deliver as much power in a short amount of time.

LFP batteries are generally cheaper to produce than NMC batteries.

LFP batteries are typically used in applications where safety and stability are important, such as electric vehicles and energy storage systems. While NMC batteries are more commonly used in portable electronic devices and power tools due to their higher energy density and peak power output.

What are the stages of manufacturing of the silicon material in PV along the supply chain, from raw material to finished modules?

Quartz, MG Silicon, Poly Silicon, Ingot, Wafer, Solar Cell, and Solar Module  


What is(are) the difference(s) between inspection and audit?

Inspection is about conformity assessment, a qualification activity with pass-fail criteria. The inspection activities mainly set the scope on products, verifying their conformity to requirements. It usually happens during the product manufacturing.

An audit activity measures by quantitative score. Its scope of work is focused on factory, mainly evaluating the capability of the supplier. Usually the audit activities are performed during the qualification phase before production starts; 

What is Pre-Production Inspection?

 Pre-Production Inspection  assesses the readiness of the factory to start the production, making sure that all conditions are right before mass-production starts. It usually includes onsite and desk activities. Its scope of work includes but not limited to manufacturing site assessment (raw material availability, process control, staff training…), testing equipment assessment (list of critical equipment, calibration, verification…) and product type assessment (product compliance, Bill of Materials, technical drawings…).

 Pre-Production Inspection helps to address the risks of unqualified production site, non-compliant raw materials, unprepared operators, and raw material shortage, etc.

What is Pre-Shipment Inspection?

During Pre-Shipment Inspection, a comprehensive range of re-tests at factories on random selection of samples (batch level, as per ISO2859, no bias) will be performed to cross-check production data. Its scope of work involves sample selection (randomly selected), retest at the factory (visual inspection, EL imaging, maximum power determination, dimensions check, and safety tests…), test analysis and review (cross-checked with manufacturing data), and replacement product check, etc.

PSI serves to tackle the risks of non-conforming products inserted in the lot, as well as falsified production and retests records.

What does the acronym “AQL” refer to?

AQL stands for Acceptable Quality Limit, an essential sampling method used in quality control. It is defined as the quality level that is the worst tolerable in ISO 2859-1. It represents the maximum number of defective units, beyond which a batch is rejected. The common AQL levels are composed of critical, major, and minor defects.

What is the ISO 2859 standard?

The ISO 2859-1 standard includes a statistical sampling scheme, which categorizes sampling frequencies into inspection levels. These inspection levels are combined with an Acceptable Quality Limit (AQL) value and organized into tables.

What is IEC 63209?

IEC TS 63209-1:2021 provides a standardized method for evaluating longer term reliability of photovoltaic (PV) modules and for different bills of materials (BOMs) that may be used when manufacturing those modules, supplementing the baseline testing defined in IEC 61215, which is a qualification test with pass-fail criteria.

What is the ISO standard that defines the sample size in Pre-Shipment Inspection ("AQL Tables")?

ISO 2859-1 specifies Sampling plans with indexed by acceptance quality limit (AQL) for lot-by-lot inspection.

What is the “5M” or “6M” method?

The “5M” or “6M” method is a quality control technique used in manufacturing and other industries, to control quality of manufacturing, or to identify and analyze the root cause of a problem. The method involves breaking down control elements into different categories, such as Man, Machine, Material, Method, Milieu (Environment) and Measurement:

Manpower – The people involved in the process
Machine – The equipment and tools used
Material – The raw materials, semi-finished goods and finished products
Method – The process and procedures followed
Milieu – External factors that may impact the process
Measurement – The data and metrics used to monitor the process

The method aims at examining each of these categories and asking questions such as, Are employees properly trained? Is the equipment in good working condition? Are there any defects? Are there any maintenance issues? And so on.

What is the Risk Priority Number method?

The Risk Priority Number (RPN) method is a risk assessment tool used in manufacturing, engineering and other industries, to evaluate and prioritize potential hazards in a process or system. The method is commonly used in the context of Failure Modes and Effects Analysis (FMEA), a structured approach to identifying and evaluating potential failure modes and their associated risks.

The RPN method assigns a numerical value to each potential hazard, based on three factors:

Severity (S) – The potential impact of the failure on safety, environment, quality, or performance
Occurrence (O) – The likelihood of the failure occurring
Detection (D) – The ease of detecting the failure before it causes harm

Each of these factors is assigned a numerical value on a scale (usually 1-10), and then multiplied together to give an overall RPN value for the hazard. The higher the RPN value, the greater the risk.

The RPN method is a quantitative approach to risk assessment, which allows for easy comparison and prioritization of hazards. It helps to identify the most critical areas that need to be addressed to ensure the safe and efficient operation of the process or system. The RPN is typically used in combination with other risk assessment methods, such as root cause analysis, to identify and evaluate risks and to develop and implement effective risk controls.

What are the 3 pillars of sustainable development?

The United Nations has identified three main areas of focus for sustainability: environmental, social, and economic. These three areas are often referred to as the “triple bottom line” of sustainability.

  • Environmental sustainability: This includes reducing the negative impact of human activities on the natural environment, such as reducing greenhouse gas emissions, protecting biodiversity, and managing natural resources in a sustainable manner.
  • Social sustainability: This includes promoting social well-being and equity, such as reducing poverty and inequality, protecting human rights, and promoting social inclusion.
  • Economic sustainability: This includes promoting economic growth and development in a sustainable manner, such as creating jobs, reducing poverty, and promoting sustainable trade and investment practices.

What are the net zero carbon scopes?

The net zero carbon scopes are the three scopes that are used to measure and track an organization’s greenhouse gas emissions and progress towards achieving net zero carbon emissions. These scopes are:

1. Scope 1: Direct emissions from sources that are owned or controlled by an organization, such as emissions from combustion of fossil fuels in boilers, vehicles, and equipment.
2. Scope 2: Indirect emissions from the generation of purchased electricity, heat, or steam that an organization consumes.
3. Scope 3: All other indirect emissions that occur in the value chain of an organization, such as emissions from the production of purchased goods and services, employee commuting, and waste disposal.

To reach net zero carbon emissions, an organization must reduce, offset, or remove all emissions within these three scopes.