Light-Induced Degradation(LID) is a phenomenon that has been extensively studied in the field of photovoltaics for some time now. It is an effect that is observed when solar module performance temporarily drops during the first hours of exposure to sunlight due to oxygen from the production process.
This phenomenon commonly produces a 1% – 3% output loss in photovoltaic cells when exposed to sunlight. While this might sound like a small amount, over extended periods of time, this small drop in performance can add up to a significant amount.
The process of light-induced degradation occurs in two steps. During the first step, oxygen atoms react with the electrons in the photovoltaic cells and create small traps in the semiconductor material. These traps are known as charge carrier traps which interfere with the normal transport of electrons in the semiconductor material.
In the second step, the trapped electrons weaken the junction between the two silicon layers that make up the solar cell, thereby reducing the efficiency of the cell.
It is important to note that not all types of photovoltaics are equally prone to LID. Amorphous silicon cells and monocrystalline silicon-based cells are some of the most common types of solar cells. While both of these are highly susceptible to the effects of LID.
Because of this, it is important for photovoltaic designers and manufacturers to consider LID. When designing and testing their cells ahead for production. If a design is found to be affected negatively by LID. Then various techniques can be employed in order to reduce its impact.
Research is also being conducted in order to develop new materials and technologies that will replace those materials most vulnerable to LID. With further advancements in this field, it is likely that LID will become a distant memory for those deploying photovoltaic cells for use in their applications.
Light-Induced Degradation (LID) is a major concern for the manufacturers and users of silicon solar cells. Which lead to a decrease in the output of generated power. It is caused by a formation of recombination active defects during forward biasing and illumination. Therefore. It is important to have an understanding of LID in order to ensure the quality of PV modules.
LID testing, which incorporates a controlled environmental light source. It helps identify and characterize any degradation that might emerge due to long-term exposure to sunlight. The aim of LID testing is to:
With LID testing, solar cell manufacturers can get more accurate performance data. Based on this data, they can make informed decisions on optimizing their cell designs and also help reduce their costs. Furthermore, LID testing provides valuable information for predictive simulations for PV system performance and system optimization. Thus ensuring the long-term effectiveness and cost-effectiveness of a PV system.
Therefore, Light Induced Degradation testing is an essential part of quality assurance for solar module manufacturers. It must be taken into strong consideration for ensuring the sustainability of solar energy. Knowing the fundamentals of LID testing can guarantee the quality and reliability of PV systems.
There are two widely-used setups for simulating field conditions for performing a LID test, both based on advanced LED technologies and electrical carrier injection.
Through the LID test, manufacturers can identify defective cells, and lower the rate of production. As well as monitor and analyze the photovoltaic performance of each cell more accurately. Since such tests can be performed relatively quickly. Test this allows the manufacturers to take immediate corrective measures and improve the production process efficiently.
The LID stabilization test is a necessary procedure used to test the degradation that PV modules will experience due to aging or environmental parameters. It is necessary to have a safety monitoring system and data logging in place to accurately measure the performance of the system.
This test consists of five main steps, each of which must be performed before the test is considered complete.
The first step is the light exposure interval. During each interval, the module is exposed to an irradiance dose of at least 5kWh/m2, with the module operating at its maximum power point (MPP).
Secondly, the temperature of the module must be correctly maintained—usually around 50°C—for optimal performance.
Thirdly, after each exposure, the module must be “flashed”, while the fourth step consists of comparing the power difference during each of the last three flashes. If the power difference passes the threshold set in the standard, then the stabilization is done and the accumulated irradiance dose is measured.
Lastly, the test will only be considered conclusive if the performance loss is lower than 5%. If this is not the case, the steps are repeated and the next light exposure interval is applied.
Due to its demands for careful preparation, strict measurements, and correct timing, carrying out the LID stabilization test require special attention. For example, extreme caution should be taken to ensure proper connections, so as not to induce any potential electrical arcs or sparks.
Likewise, the temperature in the stabilization chamber must remain at the optimum level and the light exposure intervals need to be precise. If any of these requirements are not met, the results may be misleading, compromising the accuracy of the test and the safety of personnel.
It is therefore important to be aware of the standard test conditions and precautions before attempting a LID stabilization test and having the necessary instruments, materials, and personnel qualified to deal with the task is essential. Knowing that the module has been appropriately tested and certified is essential for confidence in the system’s performance.
In conclusion, Light Induced Degradation (LID) is a phenomenon that occurs in photovoltaic cells, caused by the reaction of oxygen and electrons in the cells. This reaction creates charge carrier traps that interfere with the normal transport of electrons in the semiconductor material. These traps can have an adverse effect on the efficiency of the cells and therefore an important factor to consider when developing photovoltaic cells.
The LID standard test is an important quality assurance metric for photovoltaic (PV) module manufacturers. The test evaluates the light-induced degradation (LID) of solar modules by exposing the module to a series of light exposures of equal irradiance doses above 5kWh/ m2.
Throughout the light exposure, the module is required to operate at its maximum power point (MPP) and a constant temperature is kept at around 50°C. Generally, the test is considered complete and the accumulated total irradiance dose is measured when the module power difference in the last three flashes is smaller than the threshold value specified by the standard.
The threshold value for passing the standard test is that the performance loss must not exceed 5% after the stabilization of the light exposure intervals.
The temperature is maintained at an average of 50°C during the LID standard test.
If the module does not meet the threshold value then the module has failed the standard test.