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At least 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Voltage mapping and local defects identification in solar cells using non-contact method

Electroluminescence, infrared imaging, and current–voltage curve techniques are used to detect and map underperforming cells in a photovoltaic module or the modules in a photovoltaic string. In this work, we present a non-contact electrostatic voltmeter technique to detect and map the underperforming spots in a cell and the cells in a module. This non-contact technique directly maps the charged surface voltage (671mV) of the superstrate glass, and it had an 11-mV difference with the voltmeter values (660mV). Another data set of voltage values obtained by electroluminescence images conversion into a voltage map showed a difference of 7mV with the non-contact voltmeter values. Further, the direct voltage values obtained at various good and poor-performing spots of the cells using this technique are 3.69V and 3.79V and are validated using the voltage values obtained in electroluminescence analysis and the difference in voltage obtained by the two techniques is determined to be less than 2%. In this work, we combine the strengths of two complementary techniques of the electrostatic voltmeter (strength: quantitative) and electroluminescence (strength: spatial mapping) to obtain a quantitative spatial mapping of defects. Furthermore, this work is extendable to detect the poor-performing modules in solar PV power plants.

14 SOLAR ENERGY↗
DOE OSTI2025

Exploring Capability of Multimodal Foundation Model for Image-based Fault Detection of Photovoltaic Modules

Multimodal Foundation Model (MFM), like ChatGPT and Gemini, have emerged as powerful tools for their exceptional natural language processing capabilities and their emerging potential in image analysis. This paper investigates the application of MFMs for photovoltaic (PV) fault detection through image analysis, focusing on ChatGPT 4.0 and Gemini 1.5 Pro. Three types of PV images and the corresponding common PV faults are detected: bird droppings using visible images, cell cracks via electroluminescence (EL) images, and hotspots using infrared (IR) images. Among the two models, Gemini 1.5 Pro demonstrated superior performance, achieving near-perfect results with an average F1 score of 0.97, consistently outperforming ChatGPT 4.0 in accuracy and reliability. Unlike traditional machine learning (ML) models, MFMs can operate in a zero shot manner that does not require additional training by the user, and the input images are not limited by size, angle, scope, or PV technology. The strong adaptability and user-friendliness make MFM a promising tool for analyzing PV images and advancing health monitoring for PV modules.

Li, Baojie↗
DOE OSTI2026

Multiscale Characterization of Electrode-Induced Degradation in Perovskite Solar Cells

The stability of metal-halide-perovskite (MHP) solar cells must be understood and improved for the commercial viability of MHP technologies. Here, we apply multiscale characterization methods to study degradation modes, specifically electrode corrosion, for p-i-n MHP partial device stacks and full devices that are stored in the dark under an inert atmosphere. Our multiscale characterization approaches include full-device electro-optical performance using current-voltage (JV) curves and spatial imaging with electroluminescence (EL) and photoluminescence (PL). We further correlate interface properties using cross-sectional Kelvin probe force microscopy, which maps the nanoscale electric field properties, and electron microscopy, which demonstrates structural and chemical features. Devices stored as a full device stack degrade primarily by metal (Ag) electrode diffusion into the absorber, with formation of AgI byproducts and Ag accumulation near the indium tin oxide (ITO) contact. This causes decomposition of the perovskite absorber domains, loss of the potential drop at the electron transport layer (ETL)/perovskite interface near the metal contact, and increased equivalent resistance at the perovskite/hole transport layer (HTL) interface near the ITO contact. The devices stored without metal show a different degradation pathway dominated by corrosion of the ITO, creating voids at the ITO electrode surface with diffusion of In and Sn into the absorber. We conclude that metal electrode-induced degradation is the most severe degradation pathway under dark storage, but that ITO corrosion and absorber instability must also be mitigated. We further demonstrate mitigation of these degradation pathways by changes to the device stack, including a SnO x blocking layer at the ETL side and replacing ITO with FTO at the HTL side. These results provide a useful demonstration of specific dark degradation pathways at each electrode interface, as well as a unique multiscale example that links degradation of chemical, structural, and electrical interface properties to the full-device electro-optical characteristics.

14 SOLAR ENERGY↗
DOE OSTI2021

Mechanistic Insights to Degradation of PERC Minimodules with Differentiated Packaging Materials & Module Architectures

In this paper, we study the degradation behavior of glass-backsheet (GB) and double glass (DG) multicrystalline sil- icon monofacial PERC minimodules, fabricated using polyolefin elastomer (POE) and ethylene vinyl acetate (EVA) encapsulants, undergoing exposures of modified damp-heat (80 °C / 85% RH), with and without full spectrum light. The completed exposure time, at this time, is 1512 hours with each step of 504 hours. Step- wise measurements are conducted throughout exposures including current-voltage (I-V ) curves, Suns-V oc , electroluminescence (EL) images, and four-point proof loading with EL for tracking changes in mechanical properties in encapsulants by cell fracture probability. The results show that GB minimodules of both encapsulants, compared to DG minimodules, experience more changes in features of I-V and Suns-V oc measurements. There is no development of PV cell cracking during proof loading as seen from EL images and the load versus load line displacement plots currently.

14 SOLAR ENERGY↗
DOE OSTI2023

In-Situ Photostability Analysis of Perovskite Solar Cells by Time-Evolving Photoluminescence Imaging

In this work we investigate reversible metastabilities and irreversible degradation due to light soaking of triple-cation mixed-halide perovskite p-i-n solar cells. We use spatially resolved luminescence imaging to document the spatial inhomogeneities that exist even in high-performance devices with median efficiencies >20%. We monitor light-soaking degradation in-situ using time-evolving photoluminescence images, electro-luminescence images, and transient photovoltage. Post-stress measurements of external quantum efficiency and Kelvin- probe force microscopy suggest that long-term degradation primarily affects electrode interfaces rather than the absorber layer.

electroluminescence↗
DOE OSTI2022

Millions of Small Pressure Cycles Drive Damage in Cracked Solar Cells

Here, we applied time-varying air pressure to a PV module containing newly cracked cells. The test used a new dynamic mechanical acceleration (DMX) apparatus. We applied pressure cycles similar to natural, wind-driven cycles. Compared to standard dynamic mechanical load (DML) tests, we applied much lower pressure (10 Pa to 300 Pa RMS) and many more cycles (one million at each of four pressure levels). We present a case study on a single cell in a commercial module. We monitored electrical continuity loss across cracks using electroluminescence (EL) imaging. 10 Pa pressure cycles caused negligible change. 30 Pa pressure cycles caused permanent damage that continued worsening even after tens of thousands of cycles. After one million 30 Pa cycles, a series of 100 Pa cycles still caused new, permanent damage to existing cracks. 300 Pa cycles caused further worsening and introduced new cracks.

14 SOLAR ENERGY↗
DOE OSTI2026

UV-Induced Degradation and Associated Metastability in TOPCon Photovoltaic Modules: Understanding Kinetics and Cell Variance

Tunnel oxide passivated contact (TOPCon) silicon photovoltaic (PV) modules are dominating the PV market, but they may be susceptible to degradation under ultraviolet (UV)-containing light. Quantifying the impacts of UV-induced degradation (UVID) is complicated by an associated metastability causing further degradation under dark storage and rapid recovery under sunlight. Here, we study modules that have -2.3% to -3.2% nonrecoverable UVID loss after 60 kWh/m2 dose of 340 nm light and additional recoverable loss under dark storage. We use in situ electroluminescence (EL) imaging to characterize the post-UVID metastability at the module level. The cell-by-cell dark degradation and recovery kinetics span a wide range from +6% to -70% changes in EL intensity after 520 h of dark storage, which returns to +- 4% of the initial post-UVID EL intensity after illumination. The kinetics follow double exponential rates with dark storage degradation time constants of 345 and 45 h, and UV light recovery time constants of 5 min and 36 s. We propose that this is consistent with prior reports of kinetics for light-soaking metastability in Al2O3 passivation. Finally, we further show that cells having high UVID also have injection-dependent effective carrier lifetimes and significant intra-cell variance, suggesting possible origins of processing inconsistency.

14 SOLAR ENERGY↗
DOE OSTI2022

Degradation of Edge-Defined Film-Fed Silicon Glass–Glass Modules on Florida Rooftop After 22 Years

Thin silicon (< 100 μm) adoption can provide significantly lower cost. Kerfless technologies provide thin wafers while preventing material from being wasted. Understanding how this family of processing influences module reliability is important. A set of four edge-defined film-fed growth (EFG) silicon modules from a ten-module system in Florida is measured after 22 years of exposure. Power loss rates of 0.58–0.78% year -1 are measured for three modules, while a rate of 1.32% is measured for a module with severe delamination and corrosion. Short-circuit current degrades between 10.7% and 13.1% for all modules. Further, the losses are primarily optical and recombination based; however, series and shunt resistance effects play a non-negligible role. Pre-existing recombination losses exist but are exacerbated via degradation. Optical losses in short-circuit current are due in part to encapsulant yellowing. Electroluminescence (EL) images display the effects of processing on bulk quality by clearly showing lines of alternating brightness along the wafer length. To the authors’ knowledge, this is the first article displaying suns–V OC data, effective lifetime versus excess carrier density data, and module EL images for EFG silicon-based modules.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Hotspot testing of glass/backsheet and glass/glass PV modules pre-stressed in extended thermal cycling

This paper investigates the effect of hotspot (HS) stress endurance of two of the latest designs of monocrystalline modules: a half-cell glass/backsheet (G/B) module and a full-cell glass/glass (G/G) module. These modules have already been pre-stressed in extended thermal cycling with 600 cycles per the IEC 61215 standard to represent field-stressed modules. This study differs from the other conventional studies wherein only fresh modules are subjected to hotspot endurance stress. The G/G module reached a maximum temperature of approximately 200 °C at a cell shading of 25 %, 55 °C higher than the maximum hotspot temperature of 145 °C in the G/B module. A significant burn mark, without glass shattering, was observed in the hotspot-stressed cell of the G/G module due to the current mismatch induced by partial shading. Most of the cells in the G/G module appear to be severely damaged (severe dark areas), as observed in the electroluminescence (EL) image, while the dark regions were rarely present in the G/B module. The EL image also illustrates multiple cell cracks that resist current flow and eventually contribute to the full-cell module degradation. About 8.3 % degradation in maximum power was observed for the G/G module and 1.3 % for the G/B module after the sequential stress tests. The lower degradation in the G/B module can potentially be attributed to its design, which comprises of two parallel strings, each having 72-half-cells and benefits from lower heat dissipation. Furthermore, this indicates that the half-cell design could potentially minimize the hotspot degradation and failures in crystalline-silicon modules.

14 SOLAR ENERGY↗
DOE OSTI2021

Characterization of front contact degradation in monocrystalline and multicrystalline silicon photovoltaic modules following damp heat exposure

Reliability and durability tests play a key role in the photovoltaic (PV) industry by minimizing potential failure risks for both existing and new cell and module technologies. In this work, a detailed study of contact degradation in monocrystalline and multicrystalline PV modules is performed. The modules are subjected to a sequence of damp heat (DH) exposures followed by electrical characterization after each step. Electroluminescence (EL) imaging shows different darkening patterns for monocrystalline modules compared to multicrystalline modules; the former shows darkening near the busbars and the latter shows it across virtually the entire cell surface. The primary loss mechanism is confirmed to be resistive after comparing the current-voltage (I–V) characteristics at each DH exposure step. Representative samples have been cored out from both the degraded modules and controls for materials characterization to gain further insights into the degradation mechanism. Top-down and cross-sectional scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and top-down high-resolution X-ray photoelectron spectroscopy (XPS) analysis performed on the cored samples confirm the degradation is due to metallization corrosion. Our study suggests that the difference in the darkening pattern can most likely be attributed to the different silver paste composition used for contacting each cell technology, particularly the composition of the glass frit.

36 MATERIALS SCIENCE↗
DOE OSTI2021

A Comparison of Emerging Nonfluoropolymer-Based Coextruded PV Backsheets to Industry-Benchmark Technologies

As the photovoltaic (PV) industry is rapidly expanding around the world, there has been an increasing interest in extending the lifespan of PV modules. Concern has also emerged regarding the recyclability of modules and their component materials, including fluoropolymer-based backsheets. Laminated polyethylene-terephthalate (PET) core backsheets have traditionally been used in the PV industry, but new, coextruded polyolefin (PO) backsheets show promise as an improved alternative. In this work, minimodule and coupon samples of seven different backsheets (made of layers including contemporary PET and fluoropolymers, novel PO, and polyamide materials) were run through hygrometric- or UV photolytic-accelerated aging to identify and better understand each material's degradation modes and the backsheets' field reliability. In addition to the artificial aging, the natural weathering methods used in this article are described. The comprehensive set of chemical, mechanical, and structural characterizations at intermittent read points in this article is presented, including: visual appearance and color; gloss; mechanical tensile testing; I-V performance; electroluminescence (EL) imaging; dielectric breakdown; Fourier-transform infrared-chemical structure; X-ray-polymer structure; and differential scanning calorimetry-crystalline content. After 4000 h of aging, a strong correlation occurs between initial physical characteristics (mechanical tensile test) and operating performance (EL and I-V characteristics).

14 SOLAR ENERGY↗
DOE OSTI2025

Diagnosis of PV Cell Antireflective Coating Degradation Resulting From Hot-Humid High-Voltage Potential Aging

Corrosion of the antireflective coating on a photovoltaic cell ("ARc corrosion") has previously been observed in studies using hot-humid test conditions with external high-voltage (HV) bias. This study primarily focuses on known vulnerable legacy aluminum back surface field cells in mini-modules (MiMos) put through comparative stepped stress tests. Each cell type had MiMos at +1500 V, -1500 V, or unbiased ("Voc") potential, which were sequentially subjected to test conditions of 60 degrees C/60% relative humidity (RH) for 96 h, as in International Electrotechnical Commission Technical Specification 62804-1; 70 degrees C/70% RH for 200 h; and 85 degrees C/85% RH for 200 h. Characterizations at each step included visual camera and electroluminescence (EL) imaging, colorimetry, and current-voltage curve tracing. Final characterizations included: Suns-Voc, spatial mapping of external quantum efficiency, high-resolution photoluminescence, EL, and dark lock-in thermography imaging. Forensics were performed on extracted cores, including scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy, and scanning Auger microscopy (SAM). Forensics were also conducted on MiMos from previous studies that underwent stepped HV aging and separate outdoor aged full-sized modules. ARc corrosion was specifically seen for the glass/encapsulant/cell side of the +1500 V (HV+) stressed MiMos and modules. Appearance, color, and reflectance were the most distinguishing characteristics relative to glass corrosion, gridline corrosion and delamination, and other concurrent degradation modes. SEM/EDS and SAM identified the conversion of silicon nitride to hydrated silica, hydrous silica, or hydrated amorphous silica, which preferentially occurred at the edges and tips of the pyramidal textured cell surface.

14 SOLAR ENERGY↗
DOE OSTI2021

Reliability Implications of Solder in Multiwire Modules under Dynamic Mechanical Loading

Two generations of multiwire modules were studied under dynamic mechanical loading (DML) with in-situ differential conductance (dG) and electroluminescence (EL) imaging. Energy-dispersive x-ray spectroscopy (EDS) was used to identity the solder alloys. The earlier generation module was found to use an In-based solder alloy, and the current generation a Bi-based alloy. The earlier generation module degraded significantly under DML with increasing resistance, while the current generation module did not demonstrate degradation under DML. Atomic force microscopy scratch testing was used to probe the wear resistance of each solder alloy. These results indicate that current multiwire designs may have higher mechanical durability than earlier generations.

atomic force microscopy↗
DOE OSTI2024

Diagnosis of PV Cell Passivation Degradation Resulting from Hot-Humid, High Voltage Potential Aging

Corrosion of the antireflective coating on the cell ("AR c corrosion") was previously observed in studies using hot-humid test conditions with external high voltage (HV) bias. Because AR c corrosion is not well understood, mini-modules (MiMos) were examined in a comparative experiment using PERC and PERT as well as legacy Al-BSF cells. For separate MiMos with the cell circuit electrical at +1500 V, -1500 V, or unbiased "V oc", test conditions in the comparative study included 60degrees C/60% RH for 96 h, as in IEC TS 62804-1; 70degrees C/70%RH for 200 h; and 85degrees C/85% RH for 200 h. Characterizations at each read point included: camera and electroluminescence (EL) imaging, colorimetry, and I-V curve tracing. Characterizations at the final read point included: SunsVoc; spatially mapping external quantum efficiency (EQE); high resolution: photoluminescence (PL), EL, and dark lock-in thermographic (DLIT) imaging. Forensics were performed on extracted cores, including scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDS) and scanning Auger microscopy (SAM). Forensics were also conducted on MiMos (stepped HV aging) and full-sized modules (outdoor aging) from previous studies. AR c corrosion was specifically observed for the glass/encapsulant/cell side of +1500 V (HV+) stressed MiMos, where appearance, color, and reflectance were the characteristics most distinguished relative to simultaneously occurring degradation modes. SEM/EDS and SAM identified conversion of silicon nitride to silicon oxide or hydrous silica, preferentially occurring at the edges and tips of the pyramidal textured cell surface.

aging↗
DOE OSTI2021

Optical Detection of Crack Separation in Si PV Modules

Studying the mechanical behavior of silicon cell fractures is critical for understanding changes in PV module performance. Traditional methods of detecting cell cracks, e.g., electroluminescence (EL) imaging, utilize electrical changes and defects associated with cell fracture. Therefore, these methods reveal crack locations, but do not operate at the time or length scales required to accurately measure other physical properties of cracks, such as separation width and behavior under dynamic loads.

14 SOLAR ENERGY↗
DOE OSTI2024

Performance Assessment of Photovoltaic Panels Using Impedance Spectroscopy

The goal of this project was to develop a technique for measuring internal characteristics of a PV module using light modulation under a fixed voltage bias while measuring the resulting alternating current. This technique, light-intensity modulated impedance spectroscopy (LIMIS), has the promise of detecting early signs of panel aging and degradation that could be used for example by solar farm operators to have early warnings to repair or replace panels to maintain reliability of the overall PV array. LIMIS would be complementary with the previously developed electrochemical impedance spectroscopy (EIS), which uses an alternating voltage applied electrically to a solar cell with a similar alternating current measurement. EIS has mostly been developed for individual PV cells rather than whole modules. The project was intended to assess what different information could be revealed by LIMIS, which may in some cases be more scalable to larger modules and potentially more practical to apply in field measurements without needing to electrically disconnect PV modules. We began with small 10 W PV modules and built a testbed capable of oscillating the light intensity with frequencies up to 50 kHz. In parallel, we built a large testbed for testing large 250 W PV modules. Meanwhile, we developed procedures for established measurement techniques: current–voltage (I–V), EIS, and electroluminescence (EL) imaging, where panels are subjected to forward bias while their infrared emission is recorded using a camera modified to be sensitive to IR wavelengths. In addition, we developed protocols for accelerated aging of PV modules in two ways. Thermal cycling from –40°C to +90°C simulates the diurnal temperature cycles on a rooftop. Mechanical stress by dropping a 227 g ball from a height of 1 m simulates damage such as that due to hail impacts.

14 SOLAR ENERGY↗
DOE OSTI2025

Diagnosis of PV Cell Antireflective Coating Degradation Resulting from Hot-Humid, High Voltage Potential Aging

Corrosion of the antireflective coating on a photovoltaic cell ("ARc corrosion") has previously been observed in studies using hot-humid test conditions with external high-voltage (HV) bias. This study primarily focuses on known vulnerable, legacy aluminum back surface field (Al-BSF) cells in mini-modules (MiMos) put through comparative stepped stress tests. Each cell type had MiMos at +1500 V, -1500 V, or unbiased ("Voc") potential, which were sequentially subjected to test conditions of 60deg C/60% relative humidity (RH) for 96 h, as in International Electrotechnical Commission (IEC) Technical Specification 62804-1; 70 deg C/70% RH for 200 h; and 85 deg C/85% RH for 200 h. Characterizations at each step included visual camera and electroluminescence (EL) imaging, colorimetry, and current-voltage (I-V) curve tracing. Final characterizations included: Suns-Voc; spatial mapping of external quantum efficiency (EQE); high-resolution photoluminescence (PL), EL, and dark lock-in thermography (DLIT) imaging. Forensics were performed on extracted cores, including scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and scanning Auger microscopy (SAM). Forensics were also conducted on MiMos from previous studies that underwent stepped HV aging and separate outdoor aged full-sized modules. ARc corrosion was specifically seen for the glass/encapsulant/cell side of the +1500V (HV+) stressed MiMos and modules. Appearance, color, and reflectance were the most distinguishing characteristics relative to glass corrosion, gridline-corrosion and -delamination as well as other concurrent degradation modes. SEM/EDS and SAM identified conversion of silicon nitride to hydrated silica, hydrous silica, or hydrated amorphous silica, which preferentially occurred at the edges and tips of the pyramidal textured cell surface.

14 SOLAR ENERGY↗
DOE OSTI2025

BACKFLIP: A Comparison of Market-Benchmark Backsheet Technologies to Novel Non-Fluoro-Based Coextruded Materials and Their Correlation and Impact on PV Module Degradation Rates: Final Results of the Study at 4000 Hours or 2 Years

As the photovoltaic (PV) industry is rapidly expanding around the world, there has been an increasing interest in extending the lifespan of PV modules. Concern has also emerged regarding the recyclability of modules and their component materials, including fluoropolymer-based backsheets. Laminated polyethylene-terephthalate (PET) core backsheets have traditionally been used in the PV industry, but new, co-extruded polyolefin (PO) backsheets show promise as an improved alternative. Mini-module and coupon samples of seven different backsheets (made of layers including contemporary PET and fluoropolymers, novel PO, and polyamide (PA) materials) were run through hygrometric- or UV photolytic-accelerated aging to identify and better understand each material's degradation modes and the backsheets' field reliability. In addition to the artificial aging, the natural weathering methods used in this study are described. The comprehensive set of chemical, mechanical, and structural characterizations at intermittent read points in this study is presented, including: visual appearance and color; gloss; mechanical tensile testing; I-V performance; electroluminescence (EL) imaging; dielectric breakdown; FTIR-chemical structure; X-ray-polymer structure (WAXS); and DSC-crystalline content. After 4000 h of accelerated aging or 2y of outdoor aging, a strong correlation occurs between initial physical characteristics (mechanical tensile test) and operating performance (EL and I-V characteristics).

14 SOLAR ENERGY↗