Potential Induced Degradation Phenomenon Research Articles

Prevention of PID Phenomenon for Solar Panel Based on Mathematical Data Analysis Models

In recent years, the problem of potential-induced degradation (PID) phenomenon has been deeply associated with solar power issues because it causes serious power attenuation of solar panels and results in lowering its power generation efficiency. Thus, effectively identifying the PID problem from insights of industry data analysis to reduce production costs and increase the performance of power generation is an interesting and important subject for the solar power industry. Moreover, by the traditional standard rule (IEC62804) and the condition of a 96 h testing time, the costs of testing time and assembling materials against PID are very high and must be improved. Given the above reasons, this study proposes a hybrid procedure to organizes four mathematical methods: the mini-module testing, solar cell testing, a settling time, and a neural network, which are named as Method-1–Method-4, respectively, to efficiently solve the PID problem. Consequently, there are four key outcomes from the empirical results for solar power application: (1) In Method-1 with a 96 h testing time, it was found that the large module with higher costs and the mini module with lower costs have a positive correlation; thus, we can replace the large-module testing by the effective mini module for lower cost on module materials. (2) In Method-2 with a 24 h testing time, it was also found that the mini module and the solar cell are positively correlated; this result provides evidence that we can conduct the PID test by the easier solar cell to lower the costs. (3) In Method-3, the settling time achieves an average accuracy of 94% for PID prediction with a 14 h testing time. (4) In Method-4, the experimental result provides an accuracy of 80% when identifying the PID problem with the mathematical neural network model and are obtained within a 2 h testing time. From the above results, these methods succeed in reducing cost of materials and testing time during the manufacturing process; thus, this study has an industrial application value. Concurrently, Method-3 and Method-4 are rarely seen in the limited literature review for identifying PID problem; therefore, this study also offers a novel contribution for technical application innovation.

Potential‐Induced Degradation in High‐Efficiency n‐Type Crystalline‐Silicon Photovoltaic Modules: A Literature Review

n‐Type crystalline‐silicon (c‐Si) photovoltaic (PV) cell modules attract attention because of their potential for achieving high efficiencies. The market share of n‐type c‐Si PV modules is expected to increase considerably, with wide use in PV systems, including large‐scale PV systems, for which the system bias is set as markedly high. Such a high system bias leads to performance losses known as potential‐induced degradation (PID). By virtue of many researchers’ efforts, the PID behaviors, mechanisms, and preventive measures against PID have been well documented in conventional p‐type c‐Si modules. Researchers recently started to investigate PID in high‐efficiency c‐Si solar cells including n‐type c‐Si PV modules. Yet, the understanding of PID phenomena remains incomplete. Herein, a literature review of PID in high‐efficiency n‐type c‐Si PV modules is provided as a resource elucidating the current status of related research and remaining unresolved issues. This report mainly presents discussion of PID in several kinds of n‐type c‐Si PV modules in terms of materials science. PID phenomena are described as divided into some degradation modes. Details present a review of their respective degradation modes, degradation behaviors, proposed mechanisms, and potential measures against degradation. Remaining open issues and anticipated future studies are also summarized.

Characterization of Potential-Induced Degradation and Recovery in CIGS Solar Cells

The potential-induced degradation (PID) mechanism in Cu(In,Ga)(Se,S)2 (CIGS) thin-film solar cells, which are alternative energy sources with a high efficiency (>23%) and upscaling possibilities, remains unclear. Therefore, the cause of PID in CIGS solar cells was investigated in this study at the cell level. First, an appropriate PID experiment structure at the cell level was determined. Subsequently, PID and recovery tests were conducted to confirm the PID phenomenon. Light current–voltage (I–V), dark I–V, and external quantum efficiency (EQE) analyses were conducted to determine changes in the cell characteristics. In addition, capacitance–voltage (C–V) measurements were carried out to determine the doping concentration and width of the space charge region (SCR). Based on the results, the causes of PID and recovery of CIGS solar cells were explored, and it was found that PID occurs due to changes in the bulk doping concentration and built-in potential at the junction. Furthermore, by distinguishing the effects of temperature and voltage, it was found that PID phenomena occurred when potential difference was involved.

Behavioral Analysis of Potential Induced Degradation on Photovoltaic Cells, Regeneration and Artificial Creation

Many photovoltaic (PV) parks suffer from a decrement in their generated power capability due to a phenomenon called potential induced degradation (PID). In this paper, a regenerative system using a high step-up DC–DC converter is proposed, for regenerating PV cells that have been degraded due to the PID effect. The same device also can be used for artificially creating PID on PV panels in order to study the effects of the PID under controlled conditions. The power converter offers multiple voltage levels at the output to adapt to various voltage ratings of PV parks. The device has plug-and-play features, ultra-low cost, small size and is simple in operation. Experimental tests are conducted in real PV panels and comparative results verify the operational principles of the proposed system. The artificial creation of the PID phenomenon and the regeneration of the PV cells are successfully proven experimentally.

Effective minority carrier lifetime as an indicator for potential-induced degradation in p-type single-crystalline silicon photovoltaic modules

In this paper, we report the effective minority carrier lifetime (τeff) in fresh and potential-induced degradation (PID) acceleration tested p-type single-crystalline Si modules. τeff in different regions of solar cells was measured using the microwave photoconductance decay (μPCD) method. Electroluminescence (EL), lock-in-thermography, and dark and light current–voltage (I–V) measurements were carried out as a complementary analysis of μPCD. In addition, τeff in every stage of Si solar cell fabrication (wafer to solar cell) was measured to investigate the change of carrier dynamics. From the obtained results, a great decrease in τeff was observed in the PID-affected regions, confirming the excess non-radiative recombination centers in that region, suggesting that τeff from the μ-PCD method can be an effective indicator to judge whether PID phenomenon has occurred.

Mitigation of potential-induced degradation (PID) based on anti-reflection coating (ARC) structures of PERC solar cells

Most of solar power plants use high efficiency solar cell modules using PERC solar cells. Recently, Potential-induced degradation (PID) has been reported in which leakage current occurs due to voltage difference due to grounding, and efficiency and power are reduced within several years. In this work, we tried to change the structure of Anti-reflection coating (ARC) layer in order to mitigate PID in cell-level PERC solar cell. The ARC structure without SiO2, the structure with SiO2 on the surface, and the structure with SiO2 on the bottom are compared, and SiO2 must be located between SiNx and P-N junction to mitigate PID. In addition, PID phenomena occurring in PERC cells were tested for 96 h at 60 °C and 1000 V and used an improved method over the cell-level test method based on the TS IEC 62804-1 standard. Characteristics of PID phenomenon in solar cell were analysed by light I-V, dark I-V and electroluminescence. As a result, SiO2 must be between SiNx and P-N junctions to mitigate the PID. The PERC solar cell PID test using structural studies has mitigated PID by reducing efficiency by 0.04%, output power by 0.001 W, and shunt resistance by 11.77 Ω.

Research on Potential Induced Degradation (PID) of PV Modules in Different Typical Climate Regions

Potential Induced Degradation (PID) is one of the most important factors effecting the performances of Photovoltaic (PV) modules and PV systems in recent years. In this paper the PID phenomena of the PV power plant in different typical climate regions were studied and some experimental PID simulations were carried out in order to find out the factors effecting the performance by PID. The results show that the typical PID phenomena are easy to occur in cells close to the border of the PV module. PID phenomena can appear in PV power plants under different climate conditions, but the effecting degrees on module performance are different depending on temperature, humidity and other parameters. We also find the maximum power would recover in some degree after positive-bias voltage duration.

Effects of diffusion process on potential induced degradation of silicon solar cells.

Potential induced degradation (PID) has recently been identified as one of the most important degradation mechanisms for silicon solar cells. It is widely considered that PID is closely related with the manufacture and application period of solar modules. In this study, the effects of diffusion sheet resistance on PID were verified and explained by testing the emitter doping profile, the minority carrier lifetime, the emitter saturation current, the electrical performance of different cells, and the PID process. With increasing sheet resistance of cells, the depth and saturation current density of the emitter both decreased, and the cell efficiency increased, whereas the PID phenomenon became serious. It was found that higher sheet resistance or thinner P-N junction could lead to higher PID sensitivity. Therefore, more attention should be paid to PID phenomenon as the photovoltaic industry develops in the direction of high sheet resistance.

Degradation behavior of crystalline silicon solar cells in a cell-level potential-induced degradation test

Abstract The degradation behavior of crystalline silicon (c-Si) solar cells in a cell-level potential-induced degradation (PID) test and the effect of the test conditions are reported. The PID tests were performed in a vacuum chamber by applying a voltage of 1000 V from a temperature-controlled aluminum chuck underneath an unlaminated sample stack to the top copper electrode placed on the stack. The stack was composed of soda-lime glass, an ethylene vinyl-acetate copolymer sheet, and a conventional p-type c-Si solar cell. The investigated solar cell exhibited a large degradation of the fill factor and slight degradation of the open-circuit voltage. These degradations were mainly caused by a reduction in the parallel resistance, which is the same degradation behavior as that reported previously. This indicates that the cell-level PID test well reproduces the typical degradation behavior. However, the leakage current in the unlaminated sample stack at a relatively low temperature exhibited a different temperature dependence from that in a laminated sample stack. The difference in the temperature dependence was caused by temperature-dependent contact resistances within the unlaminated sample stacks. This indicates that there is a difference between the temperature dependences in cell-level and module-level PID tests. This difference in the temperature dependence was reduced by the use of a heavier top electrode. These findings may assist in choosing the proper test conditions for this kind of cell-level PID test. A cell-level PID test for an n-type front-emitter c-Si solar cell was also performed. A typical degradation behavior, characterized by reductions in the open-circuit voltage and the short-circuit current, was observed, which implies that this test can be widely applied to PID phenomena occurring in many kinds of solar cells.

Influence of crystal defect density of silicon wafers on potential-induced degradation (PID) in solar cells and modules

Potential-induced degradation (PID) was recently identified as one of the most important degradation mechanisms. It can be due to many different reasons during the manufacture and application of solar energy system. In this study, the effect of defect density of silicon wafers on the PID phenomenon is revealed by PID simulation tests at both the cell and module levels. Silicon wafers of the same and different crystal structures with various defect densities are studied, respectively. The results, which are coincident, showed that the extent of PID has a positive correlation with defect density. The increased defect density can lead to a drastic decline in Rsh, finally promoting the PID phenomenon. Silicon wafers with the lowest defect density demonstrate the least current leakage and highest PID resistance after PID simulation tests. Therefore, the result of this study shows the correlation between the PID strength of solar cells and defect density of silicon wafers, which can be easily measured during wafer manufacture.

Potential-induced degradation of thin-film Si photovoltaic modules

Potential-induced degradation (PID) of thin-film Si photovoltaic (PV) modules was investigated. The characteristics of PID phenomena of thin-film Si PV modules are markedly different from those of crystalline Si PV modules. Not only performance loss but also linear-shape and spot-shape delamination was observed after negative voltage application. Recovery from PID was also observed after positive voltage application. However, rapid progression of PID was found after the second negative voltage application after recovery from the initial PID. The root cause of PID of thin-film Si PV modules is thought to be the delamination between a transparent conductive oxide film and a glass substrate. Such degradation accompanied by delamination was also observed in thin-film Si PV modules exposed outside for about 5 years.

Microscopic aspects of potential-induced degradation phenomena and their recovery processes for p-type crystalline Si photovoltaic modules

Processes for potential-induced degradation (PID) and recovery phenomena were characterized using p-type multicrystalline Si photovoltaic modules and by PID test method using Al plate. Very severe PID phenomena accompanied with a drastic reduction in both open-circuit voltage and shunt resistance were observed within only several hours. It was found that PID phenomena are strongly accelerated at higher temperature and under higher negative-voltage application, on the other hand, PID phenomena do not necessarily require high humidity in this test method using Al plate. Na diffusion from the cover glass to the Si cell was observed after PID test. Recovery process from PID was also observed by applying positive voltage. However, complete recovery of photovoltaic performances was observed at room temperature in the dark without positive-voltage application for test modules with PID although recovery process requires a few hundred days.

Prediction of the Potential Induced Degradation of Photovoltaic Modules Based on the Leakage Current Flowing Through Glass Laminated With Ethylene-Vinly Acetate

In the potential induced degradation (PID) phenomenon, the output power of a photovoltaic (PV) module decreases due to the high potential difference between the PV system and the ground. This voltage forcefully moves the positive charge in the module to the surface of the solar cell. The accumulated charge leads to the performance deterioration of the module, namely, PID of the module. We conducted a study to accurately predict the output reduction of the module operating in various installation conditions coming from the PID phenomenon. We investigated the leakage current flowing through front glass laminated with encapsulation material simultaneously exposed to various performance conditions of the PV system, namely, relative humidity, temperature, and applied voltage, which have an important effect on the PID of the module. The degradation of the module coming from PID was calculated on the basis of the obtained leakage current. To confirm the calculated data, modules with one solar cell were manufactured and the power loss results of the modules' exposure to various PID generation experiments were compared with the expected results. The results showed that we could predict the degradation of the modules by PID within a 2% tolerance under the PV system installation conditions.

Relationship between cross-linking conditions of ethylene vinyl acetate and potential induced degradation for crystalline silicon photovoltaic modules

In this study, we investigated the relationship in crystalline silicon (c-Si) photovoltaic (PV) modules between the cross-linking level of copolymer of ethylene and vinyl acetate (EVA) as the encapsulant and the degree of degradation due to potential induced degradation (PID) phenomenon. We used three methods for the determination of cross-linking level of EVA: xylene method, which is one of the solvent extraction methods (SEM), curing degree by differential scanning calorimetry (DSC), and viscoelastic properties by dynamic mechanical analysis (DMA). The results indicate that degradation of PV modules by PID test depends on the cross-linking level of EVA. The PV modules encapsulated by EVA with higher cross-linking level show lower degradation degree due to PID phenomenon. Also we showed that EVA with higher cross-linking level tended to be higher volume resistivity. This tendency is similar to that for electrical resistance value during the PID test. The PID test was also done by changing thickness of EVA between front cover glass and c-Si with the same cross-linking level. The PV modules encapsulated by thicker EVA between front cover glass and c-Si cell show lower degradation by PID. From these results, the PV modules encapsulated by EVA with higher cross-linking level, higher volume resistivity and increased thickness would be tolerant of PID phenomenon.

태양전지 모듈의 구성 요소가 PID 발생에 미치는 영향

PID (potential induced degradation) of PV module is the degradation of module due to the high potential difference between the front surface of solar cells and ground when PV modules operate under high humidity and temperature conditions. PID is generally derived from the positive sodium ions in front glass that are accumulated on P-type solar cells. Therefore, some papers for the electrical characteristic of only front components as glass, EVA sheet, solar cell under PID generation condition were revealed. In this paper, we analyzed the different outputs of module with PID by considering the all parts of module including the back side elements such as glass, back sheet. Mini modules with one solar cell were fabricated with the various parts on front and back sided of module. To generate PID of module in a short time, the all modules were applied.1,000 V in , 85% RH. The outputs, dark IV curves and EL images of all modules before and after experiments were also measured to confirm the main components of module for PID generation. From the measured results, the outputs of all modules with front glass were remarkably reduced and the performances of modules with back and front glass were greatly deteriorated. We suggest that the obtained data could be used to reduce the PID phenomenon of diverse modules such as conventional module and BIPV (building integrated photovoltaic) module.