Before and after any qualification test, a solar module must be in a defined, electrically stable state. Without stabilization, power output measurements are unreliable, and test results cannot be meaningfully compared. The IEC 61215 MQT 19 stabilization procedure defines exactly how that stable state is achieved and verified. Here is a complete breakdown of what the test involves.
What is MQT 19 Stabilization?
MQT 19, defined in IEC 61215-2:2021, is a foundational test that underpins the validity of the entire IEC 61215 qualification sequence. Its principle is simple:
All PV modules need to be electrically stabilized. For this purpose, all modules shall be exposed to a defined procedure, and the output power shall be measured directly afterwards. This procedure and output power measurement shall be repeated until the module is assessed to have reached an electrically stable power output level.
Where light is used for stabilization, simulated solar irradiance is preferred over natural light.
MQT 19 consists of three sub-tests, each applied at a different point in the test sequence:
• MQT 19.1 — Initial stabilization
• MQT 19.2 — Final stabilization
• MQT 19.3 — Stress-specific stabilization (BO-LID)
Stabilization Criterion
The following formula is used to assess whether a module has reached its stabilized electrical power output:
(P_max − P_min) / P_average < x
where P_max, P_min, and P_average are the extreme and average values of three consecutive output power measurements P₁, P₂, and P₃ taken from a sequence of alternating stabilization and measurement steps using MQT 02. P_average is the average of all three. STC output power is determined using MQT 06.1.
The value of x is defined in the technology-specific parts of this standard series.
Light-Induced Stabilization Procedures
Apparatus for Indoor Stabilization
• A Class CCC solar simulator or better, in accordance with IEC 60904-9
• A suitable reference device with integrator for monitoring the irradiation
• Means to mount the modules as recommended by the manufacturer, co-planar with the reference device
• The reference device is used to set the irradiance between 800 W/m² and 1000 W/m²
• During simulator exposure, module temperatures shall stay in the range of (50 ± 10) °C. All subsequent stabilizations shall be done at the same temperature as the initial, within ±2 °C
• Temperature monitoring to an accuracy of ±2.0 °C and repeatability of ±0.5 °C; the sensor shall be mounted on a representative position for the average module temperature
• A resistive load sized so the module operates near its maximum power point, or an electronic maximum power point tracker (MPPT)
Requirements for Outdoor Exposure
• A suitable reference device with integrator for monitoring irradiation
• Means to mount the modules as recommended by the manufacturer, co-planar with the reference device
• Only irradiance levels above 500 W/m² count toward the total irradiance dose required to check stabilization; temperature limits are specified in the technology-specific parts
• Temperature monitoring to an accuracy of ±2.0 °C and repeatability of ±0.5 °C
• A resistive load or MPPT sized so the module operates near its maximum power point
Procedure
1. Measure the output power of each module using the maximum power determination procedure at any convenient module temperature within the allowable range that can be reproduced within ±2 °C for future intermediate measurements.
2. Attach the load to the modules and mount them as recommended by the manufacturer, with the reference device in the test plane of the simulator.
3. Record the irradiance levels, integrated irradiation, temperature, and used resistive load of the module.
4. Subject each module to at least two intervals of irradiation as defined in the technology-specific parts until its maximum power value stabilizes.
5. Measure the output power using MQT 02. The time period between light exposure and final maximum power determination is specified in the technology-specific part.
6. Intermediate measurements of MQT 02 shall be performed in approximately equal integrated irradiation dose intervals. All intermediate maximum power measurements shall be performed at any convenient module temperature reproduced within ±2 °C.
7. Report the integrated irradiation and all parameters at which stability is reached. For outdoor procedures, where applicable, state the type of load used and show temperature and irradiance profiles.
Other Stabilization Procedures
Other stabilization techniques, such as applying current or voltage bias, can be used after validation. It is known that the application of current or voltage bias can lead to similar effects in solar cells as light exposure. Such alternate stabilization procedures are provided by the manufacturer.
Validation process for alternate procedures:
Alternate procedures can be used instead of light exposure if validated with three modules in sequence A as initial stabilization:
1. Perform the alternate procedure.
2. Measure MQT 06.1 after the minimum and no more than the maximum time specified in the technology-specific parts.
3. Perform indoor light-induced stabilization procedure in accordance with technology-specific requirements.
4. Measure MQT 06.1 again after the minimum and maximum time specified.
An alternate method is considered valid if the two MQT 06.1 measurements are within 2% for all three evaluated modules. If one module does not meet this criterion, the method is not validated.
MQT 19.1 — Initial Stabilization
Initial stabilization is performed following the procedure and requirements defined in MQT 19. Stabilization is reached when the criterion in the stabilization formula above is fulfilled.
The initial stabilization is performed to verify manufacture label values as defined in the pass criterion (Gate No. 1). The number of modules subjected to MQT 19.1 is defined in the technology-specific parts.
MQT 19.2 — Final Stabilization
Final stabilization is performed following the same procedure and requirements as MQT 19. Stabilization is reached when the criterion is fulfilled.
The final stabilization is performed to determine module degradation during the test as defined in the pass criterion (Gate No. 2). Unless otherwise stated, all modules from Sequences A and C to E must undergo MQT 19.2 testing.
MQT 19.3 — Stress-Specific Stabilization (BO-LID)
Purpose
Some stress conditions may change the state of semiconductor defects in a way that is not representative of field behavior and is not related to the degradation mechanisms targeted by the stress tests. In this case, a stress-specific stabilization may be required to set the defects into a reproducible state before or after stress.
MQT 19.3 describes a stabilization procedure that puts the defects causing boron-oxygen light induced degradation (BO-LID) into the regenerated state. It shall only be used at points in the test flow specifically prescribed for this purpose.
Apparatus
• A climatic chamber with automatic temperature control
• Mounting means that allow free circulation of surrounding air; thermal conduction of the mount or support shall be low so that modules are thermally isolated
• Measurement instrumentation with accuracy of ±2.0 °C and repeatability of ±0.5 °C for recording module temperature
• Means for applying, throughout the test, a current equal to the module short-circuit current I_sc
Procedure
1. Install the module(s) at room temperature in the climatic chamber.
2. Connect the temperature-monitoring equipment to the temperature sensor(s). Connect each module to the appropriate current supply by connecting the positive terminal of the module to the positive terminal of the power supply and the second terminal accordingly.
3. Close the chamber and apply a current of I_sc ± 5% to each module. As long as the current applied to each module is within 5% of its I_sc, the currents applied through multiple modules in one chamber need not be the same.
4. Increase the climatic chamber setpoint such that the temperature of each module reaches (80 ± 5) °C, and never exceeds 85 °C.
5. Maintain the current and temperature within the prescribed limits for (48 ± 2) hours.
Why MQT 19 Matters for PV Module Certification
Stabilization is the foundation on which all other IEC 61215 measurements rest. A module that has not reached a stable power output state will yield different power readings depending on its recent light exposure history — making it impossible to accurately assess degradation through the test sequence. Without MQT 19, Gate No. 1 (label verification) and Gate No. 2 (degradation assessment) in IEC 61215-1 would be meaningless.
The addition of MQT 19.3 (BO-LID) reflects the industry's growing understanding of light-induced degradation mechanisms, particularly in PERC and boron-doped silicon cells where boron-oxygen defects are a real-world concern. By requiring modules to be in a reproducible regenerated state before stress tests, the standard ensures that test results reflect genuine stress-induced degradation rather than artefacts of the diode's defect state.
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Source: IEC 61215-2:2021 — Terrestrial photovoltaic (PV) modules – Design qualification and type approval – Part 2: Test procedures, Section 4.19