Potential Induced Degradation Research Articles

Broad-Scale Electroluminescence Analysis of 5 Million+ Photovoltaic Cells for Defect Detection and Degradation Assessment

This paper presents a comprehensive study on the detection, classification, and impact of defects in photovoltaic (PV) modules, using Electroluminescence (EL) imaging as the primary diagnostic tool. The study inspects 85,000 PV modules across 167 installations over a nine-year period, with defects categorized into line cracks, complex cracks, edge-ribbon cracks, and Potential-Induced Degradation (PID). A key finding reveals an increasing prevalence of complex and edge-ribbon cracks in recent installations, highlighting potential shifts in manufacturing or installation processes. Despite these observed defects, the degradation rates of the PV systems remain below 1% per year, with long-term projections indicating that most systems will retain over 80% of their original capacity after 25 years. This study underscores the importance of early defect detection for maintaining system efficiency and longevity, and its findings are crucial for refining manufacturing and installation standards. Novel insights include the integration of EL imaging for defect classification and the suggestion of semantic segmentation techniques to further improve automated defect detection. These advancements hold the potential to optimize the predictive maintenance of PV systems, ensuring enhanced performance and reduced operational losses over time.

Characterization of rear-side potential-induced degradation in bifacial p-PERC solar modules

Bifacial solar modules are increasingly preferred over monofacial modules to maximize the solar power output within a limited space. Owing to their high efficiency and compatibility with existing production lines, bifacial p-type passivated emitter and rear contact (p-PERC) solar modules have dominated the market since their commercialization. This study analyzes the influence of Al2O3, a passivation layer of p-PERC solar cells, on the PID and its underlying mechanism. Experiments were conducted on bifacial p-PERC module samples to analyze their electrical properties. Additionally, cell-like samples were fabricated to measure characteristics, for example, carrier lifetime, that are difficult to assess in full modules. To accelerate module degradation, experiments were conducted at 85 °C and 85 % humidity, while a voltage of −1000 V was applied to investigate the PID phenomenon. The results reveal degradation at the rear of the module caused by polarization effects, which were confirmed through changes in solar cell parameters and recombination current. The proposed mechanism indicates that the degradation in bifacial p-PERC solar modules is caused by the field-effect deterioration of the Al₂O₃ layer caused by alkali ions diffusing from the glass. This is observed through changes in the carrier concentration within Si and the detection of alkali ions within Al2O3. Our analysis considers both module and cell structure samples to delineate the influence of Al2O3 on the PID, which has not been previously reported. This study enhances the understanding of the polarization effect in bifacial p-PERC solar cells, thus contributing to the advancement of solar cell passivation strategies.

Performance evaluation of inorganic Cs3Bi2I9-based perovskite solar cells with BaSnO3 charge transport layer

This research embedded with a novel idea of integration of perovskite material as charge transport layer corresponding to the perovskite absorber layer. The study explores the effectiveness of BaSnO3 perovskite material as an electron transport layer (ETL) in Cs3Bi2I9-based perovskite solar cells, using SCAPS-1D simulations. The research meticulously examines how structural and optical variations in each layer affect the device’s performance indicators, finding the thickness of the Cs3Bi2I9 layer and its defect concentration pivotal for optimal functionality. The highest photovoltaic efficiency, 20.62%, was achieved with an absorber layer thickness of 0.8 micrometers and acceptor and donor concentrations between 1E17 /cm3 and 1E18 /cm3, respectively. The absorber’s bulk defect density optimally ranged from 1E14 /cm3 to 1E15 /cm3. Interface defects between BaSnO3 and Cs3Bi2I9 layers significantly influenced performance, more so than those at the HTL (Cu2O) interface. The study also assesses thermal effects and series and shunt resistances, aiming to mitigate potential induced degradation (PID), a key concern for solar cell longevity and reliability. Nickel (Ni) was chosen as the back contact metal, balancing cost and efficiency. This research intends to clarify PID conditions to enhance the durability and consistent performance of photovoltaic systems.

Polymer encapsulation impact on potential-induced degradation in PV modules revealed by a multi-modal field study

Potential-induced degradation is a significant issue affecting the performance and reliability of photovoltaic systems, particularly in large-scale installations. Understanding the mechanisms underlying the formation of potential-induced degradation is crucial for developing effective mitigation strategies and ensuring the long-term sustainability of solar energy technologies. During the inspection of a 1.2 MWp photovoltaic power plant, various imaging methods, electrical measurements, spectroscopic characterization methods, and monitoring data analyses were utilized and combined. We observed that two percent of the photovoltaic modules at the string ends exhibited the characteristic checkerboard pattern in infrared or electroluminescence imaging, implicating issues on twelve percent of all strings. This uneven distribution of potential-induced degradation-affected modules suggests additional key factors are at play. Investigations of the backsheet and ethylene-vinyl acetate using near-infrared reflectance analysis revealed that one backsheet type and two different ethylene-vinyl acetate types were present in the installed solar panels. Yet, only one type of ethylene-vinyl acetate correlated with potential-induced degradation. The same type also exhibited a higher rate of oxidative degradation. Scanning electron microscopy and energy-dispersive X-ray spectroscopy revealed a significantly increased sodium ion content in the ethylene-vinyl acetate and glass of the potential-induced degradation-affected modules. Our findings highlight the crucial role of polymer encapsulation in the development of potential-induced degradation and underscore the importance of careful polymer selection in the design of photovoltaic module technologies.

Investigating the impact of humidity on potential-induced degradation (PID) in photovoltaic modules with ash accumulation

Investigating the impact of humidity on potential-induced degradation (PID) in photovoltaic modules with ash accumulation

Effect of Accumulated Dust Conductivity on Leakage Current of Photovoltaic Modules

Photovoltaic (PV) modules are often situated in hot and windy environments, such as deserts, where dust accumulation poses a significant problem. The build-up of dust can result in an increase in PV module leakage current, making the modules more vulnerable to potential-induced degradation (PID), ultimately leading to a reduction in the efficiency of PV power generation. In this study, we investigate the impact of dust accumulation on the surface of PV modules on leakage current. A dust model is developed based on the Arrhenius relation, taking into account the impact of temperature and density on dust conductivity. The equation for leakage current due to dust accumulation is derived based on the clean module leakage current equation. We undertake a simulation of natural conditions in a laboratory setting to analyze the impact of dust on the leakage current of photovoltaic modules. The results show the following: At high temperatures, the leakage current will significantly increase due to the elevated conductivity of the dust. The conductivity increased by 27.1%, 48.9%, 64.3%, and 118% for the four groups of dusty PV modules, respectively. Leakage current prediction has a better accuracy when dust is equated to series conductance. Dust can reduce the activation energy of PV modules by up to 3.48%.

Method to Study Potential‐Induced Degradation of Perovskite Solar Cells and Modules in an Inert Environment

The efficiency of perovskite solar cells (PSCs) is advancing rapidly, yet their sensitivity to ambient conditions poses challenges. An additional degradation mechanism, potential‐induced degradation (PID), can emerge during field operation, but the understanding of PID within perovskite devices is limited. To exclude environmental stressors, this study is conducted in an inert environment at room temperature. PSCs and mini‐modules are subjected to a 324 h PID stress test at −1000 V, revealing relative efficiency losses of around 29% and 24% for the PSCs and mini‐modules, respectively, exposing subtle degradation differences. These degradation rates are notably lower than reported in the literature, suggesting possible additional degradation pathways arising from suboptimal encapsulation combined with ambient conditions. Subsequently, half of the stressed samples are subject to +1000 V for 523 h and recover to a reduced efficiency loss of 15% and 7.7% for the PSCs and module, respectively. In contrast, storing the stressed samples on the shelf increased the efficiency losses to 32% (PSCs) and 41% (module). Therefore, the post‐PID rates differ significantly between both groups, whereas both effects of voltage recovery and progressed degradation are more pronounced in modules compared to cells. This study contributes to a robust method for PID research.

PID Evaluation of Transparent Backsheet Modules

This Work Deals with the Robustness of Transparent Backsheet Modules using Coating/PET/PVF (TPC) Polymer Layers when Exposed to an Extended Potential Induced Degradation (PID) Stress based on IEC 61215. Results show a Significant Power Decrease on the Front Side after 576h of Testing for Negative Voltage with Three Time more Impact at the Rear Side Despite the Absence of Glass. PID is Confirmed with Electroluminescence (EL) and Photoluminescence (PL). Measurements Showing the Appearance of Dark Areas on Several Cells and an Inhomogeneous Signal all Along the Module with “Light trails”. Moreover, Transmission Electron Microscopy Measurement Points out Sodium Presence at Both Cell Interface Despite POE Encapsulant and the Absence of Glass at the Rear Side. Two Types of PID Seem to be Present: Low Light Current-Voltage Measurements Suggest the Presence of PID-Potential at the Rear Side of the Cells And the Dark Area Could Be linked To PID-Corrosion Effect as Depassivation is observed with EL and PL.

Flexible silicon solar cells with high power-to-weight ratios.

Silicon solar cells are a mainstay of commercialized photovoltaics, and further improving the power conversion efficiency of large-area and flexible cells remains an important research objective1,2. Here we report a combined approach to improving the power conversion efficiency of silicon heterojunction solar cells, while at the same time rendering them flexible. We use low-damage continuous-plasma chemical vapour deposition to prevent epitaxy, self-restoring nanocrystalline sowing and vertical growth to develop doped contacts, and contact-free laser transfer printing to deposit low-shading grid lines. High-performance cells of various thicknesses (55-130 μm) are fabricated, with certified efficiencies of 26.06% (57 μm), 26.19% (74 μm), 26.50% (84 μm), 26.56% (106 μm) and 26.81% (125 μm). The wafer thinning not only lowers the weight andcost, but also facilitatesthecharge migration and separation.It is found thatthe 57-μm flexible and thin solarcell shows the highest power-to-weight ratio (1.9 W g-1) and open-circuit voltage (761 mV)compared to the thick ones. All of the solar cells characterized have an area of 274.4 cm2, and the cell components ensure reliability in potential-induced degradation and light-induced degradation ageingtests. This technological progress provides a practical basis for the commercialization of flexible, lightweight, low-cost and highly efficient solar cells, and the ability to bend or roll up crystalline silicon solar cells for travel is anticipated.

Prevention of potential‐induced degradation using a moisture barrier in crystalline silicon photovoltaic modules

AbstractAs photovoltaic (PV) modules are exposed to high temperatures and humidity over time, they generate leakage current, which leads to potential‐induced degradation (PID) and lower power output. In silicon, Cu(In,Ga)(Se,S)2 (CIGS) thin film and perovskite solar cells, PID has been shown to be driven by the presence of Na in the module glass. PID stability is crucial for the commercialization of such solar modules. This study aims to confirm the leaching phenomenon of Na in soda–lime module glass and study the use of polytetrafluoroethylene (PTFE) as a moisture barrier to prevent PID. By water immersion and exposure to different temperature and humidity conditions, we exhibited Na leaching in soda–lime glass. Moreover, we demonstrate the use of an anti‐PID moisture barrier made of PTFE, which was deposited using kinetic spraying between the cover glass and encapsulant in the solar module. The thickness of the moisture barrier was controlled by adjusting the deposition rate, and the PID characteristics were evaluated by manufacturing solar modules for different barrier thicknesses. Light current–voltage (LIV), dark current–voltage (DIV), and electroluminescence (EL) measurements confirmed that the PTFE moisture barrier effectively inhibits the degradation of solar cells. This study provides further insights into the Na leaching phenomenon and PID mechanism in PV modules and contributes to the design and development of more stable solar cells.

Comprehensive analysis of aging mechanisms and design solutions for desert-resilient photovoltaic modules

This study aims to address the best practices and recommendations that contribute to the development of a tailored photovoltaic (PV) module design suited to desert conditions. To realize this customized design, a comprehensive analysis of in-situ aging assessment on five PV systems was undertaken. The initial phase of this assessment involved outdoor visual inspections, revealing visual material degradation modes such as snail trails, delamination, and discoloration. Subsequently, using infrared (IR) imaging and electroluminescence (EL) as powerful techniques, we pinpointed non-visual material issues such as hot spots, potential-induced degradation (PID) on p-type crystalline PV module, and micro-cracks emerging. The trends in the electrical parameters obtained from outdoor-measured I–V curves are analyzed to delve deeper into the performance decline of the PV modules. The findings revealed elevated degradation rates (Rd) values up to 2.7 %/y, largely attributed to the severe climate conditions at the investigation site. This poses significant implications for PV economic viability of the power plant and the payback time in such conditions. By focusing on the key material-related degradation modes that prevail in the exposed five PV systems employing a methodology that leverages Pareto analysis and integrates severity scores assessed by the National Renewable Energy Laboratory (NREL), we analyzed various mitigating solutions to address the dominant observed defects under the challenging desert conditions. Some recommendations on the constitutive parts of the module have been proposed to make them more resilient to the desert environment. These mitigating solutions include recommendations for enhancing the durability of the components of the module to better withstand the harsh desert environment.

Potential-induced degradation: a challenge in the commercialization of perovskite solar cells

Potential-induced degradation, a major factor in solar cell stability, is a reliability threat that can damage them within a shorter timeframe. As a promising and emerging PV technology, perovskite solar cells must overcome PID to be commercialized.

Potential-induced degradation phenomena in single-encapsulation crystalline Si photovoltaic modules

This paper particularly explains potential-induced degradation (PID) of wafer-based standard p-type crystalline silicon technology. We present a single-encapsulation method that is useful for simulating PID in the laboratory to facilitate microanalyses of module-level solar cells. The PID testing is performed for the module with single-encapsulation and conventional modules. Their current–voltage characteristics and electroluminescence images are investigated before and after the PID tests. As described herein, we infer that the single-encapsulation modules generate PID almost in the same way as conventional modules do, and that the degradation trend is almost identical to that of conventional modules. Results of PID recovery tests indicate that the time necessary for PID recovery is always less than that for PID generation, irrespective of the encapsulation method.

Delay of the potential-induced degradation of n-type crystalline silicon photovoltaic modules by the prior application of reverse bias

We investigated the influence of the pre-application of reverse bias on the potential-induced degradation (PID) of n-type front-emitter (n-FE) crystalline Si (c-Si) photovoltaic modules. Applying a prior positive reverse bias to n-FE cells delays charge-accumulation-type PID (PID-1), decreases in short-circuit current density (J sc) and open-circuit voltage (V oc). The prior positive bias accumulation may accumulate negative charges in the SiN x , which leads to an increase in a duration for the positive charge accumulation by the PID test applying a negative bias. We also found that sufficiently long prior positive bias application results in the delay of PID-2, a fill factor reduction by the incursion of Na ions into the depletion region of the p–n junction of n-FE cells.

Unveiling the Potential of Infrared Thermography in Quantitative Investigation of Potential-Induced Degradation in Crystalline Silicon PV Module

Potential-induced degradation-shunting (PID-s) is a severe degradation mechanism in photovoltaic (PV) cells that significantly impacts module performance. Regular monitoring and quantitative assessment of PID-s are crucial for ensuring long-term reliability of PV systems. Current-voltage (I-V) characteristics and electroluminescence (EL) imaging are commonly used for quantitative performance evaluation of PID-s affected PV modules. However, conducting I-V measurements is time-consuming when performed across large PV installations, while EL imaging has limitations for severely PID-s affected cells with no EL emission. This article proposes the use of inverse infrared (IRINV) thermography as an alternative investigation technique for PID-s in a PV module. IRINV imaging is fast and also effectively maps the severely PID-s affected cells in a PV module. This article unveils the potential of IRINV thermography in quantitative investigation of PID-s in crystalline silicon PV modules. The module level investigations present insights into the correlations between cell temperature and power output under different imaging conditions using Pearson correlation. Results indicate that steady-state operation with medium input current provides the most suitable condition for quantitative PID-s investigation. Furthermore, cell level analysis of temperature distribution and its variation with PID-s progression has been investigated using histogram and kernel density estimation (KDE) statistical tools, revealing distinct patterns as PID-s progresses. A PID-s severity index is proposed based on KDE, providing a quantitative measure of PID-s severity in cells within a PV module. This work provides valuable insights into the use of IRINV thermography as an alternative technique for assessment of PID-s in PV module inspection.

A potential induced degradation suppression method for photovoltaic systems

Potential induced degradation (PID) is regarded as one of leading causes of photovoltaic (PV) module degradation. A PID suppression method is proposed in this paper, in which a PID suppression unit is added between DC negative bus and ground. The idea is to regulate the output voltage of the added power supply, and then correspondingly raise the voltage of the PV module to the ground to suppress the PID effect. A high-value resistor is added in the proposed PID suppression unit for the safety of preventing electric shock. To determine the value of the high-value resistor, detailed analysis for PV module positive or negative terminals shorted to the ground is performed. The design of the added power supply is investigated, including topology selection, voltage setting, and close-loop control. Furthermore, detailed voltage analysis for the added power supply is implemented for the systems with front-end boost DC/DC converters and 3-level boost DC/DC converters, respectively. Additionally, in the proposed solution, a switch is used to control whether the PID suppression unit is connected to the system. Three requirements are explained, as well as the corresponding control for the switch. Finally, experimental results are presented to validate the proposed theory.

Highly Improved PID Stability for Cu(In,Ga)Se2 Solar Modules Due to a Filled P1 Groove

Two types of Cu(In,Ga)Se2 (CIGS) thin-film solar modules, differing only in the patterning procedures, were exposed to a high voltage (1 kV) across the thickness of the soda-lime glass substrate. Both module types utilized a cell stack, and in particular, a molybdenum back contact, which was optimized for CIGS solar cells with enhanced stability against potential-induced degradation (PID). A standard module with regular patterning lines for monolithic interconnection consists of P1, P2, and P3 lines, with P1 separating the back contact, P2 establishing the contact between the front contact TCO of one cell to the Mo back contact of the next cell, and P3 isolating the front contact from one cell to the next cell. However, modules employing this cell stack with regular patterning lines P1, P2, and P3 suffered considerably from PID while modules with a P1 groove filled with an insulator showed greatly enhanced stability similar to the pure single cell without P1 patterning. PID manifests once a specific quantity of charge has been transmitted through the soda-lime glass substrate, while the molybdenum back contact of the cell functions as the cathode, maintaining a negative bias relative to the substrate’s backside. As a consequence of PID, sodium is increased in the adsorber for susceptible cells. Therefore, inhibiting sodium transport through the P1 groove by filling it with an insulating material enhances the PID stability of the modules considerably. As a result, the modules with a filled P1 groove showed similar stability to the single solar cells with an improved PID stable cell stack, while modules without a filled P1 patterning were much more susceptible to PID, although a cell stack with greatly enhanced PID stability was used. In summary, the presented strategy to fill the P1 groove offers a viable and novel path to improved PID stability of CIGS modules.

Enhancing solar photovoltaic modules quality assurance through convolutional neural network-aided automated defect detection

Detecting cracks in solar photovoltaic (PV) modules plays an important role in ensuring their performance and reliability. The development of convolutional neural networks (CNNs) has introduced a game-changing dimension in the detection of defects in PV modules. This paper proposes an automated defect detection method for PV, by leveraging custom-designed CNN to accurately analyse electroluminescence (EL) images, identifying defects such as cracks, mini-cracks, potential induced degradation (PID), and shaded areas. The proposed system achieves a high level of validation accuracy of 98.07%, reducing manual inspection demands, enhancing quality standards, and saving costs. The system was validated in a case study for PV installations faulty with PID, where it identified all defective modules with a high degree of precision of 96.6%, surpassing existing methods. This methodology holds promise for revolutionizing PV industry quality control, improving module reliability, and supporting sustainable solar energy growth.

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.

Mitigation of Potential‐Induced Degradation in Glass‐Encapsulated Perovskite Solar Cells Using a NiOx Barrier Layer

While the efficiency of perovskite solar cells has been increasing rapidly in recent years, studies on potential‐induced degradation (PID) in these devices have so far been very limited. Herein, the first successful mitigation of PID in glass‐encapsulated perovskite solar cells is reported. A thin NiOx blocking layer between the indium tin oxide and the self‐assembled monolayer is proposed to suppress the PID in these solar cells. Two groups of devices are fabricated, with and without the presence of the NiOx layer. When −1000 V is applied between the short‐circuited solar cell and the front glass pane, the original devices without NiOx only retain about 27% of the initial efficiency, and the modified devices with NiOx retained ≈65% after an extended stress duration of 96 h. The Na+ ions from the glass pane occupy NiOx vacancies under high voltage stress and, as a result, the Nax ion migration toward the perovskite layer is heavily suppressed due to the introduction of NiOx. The modified devices also demonstrate good long‐term stability, retaining more than 80% of initial efficiency after the PID stress test. The results of this work are helpful on the journey toward successful commercialization of perovskite solar cells.