Encapsulation of Solar Cells for Damp Heat Test

Moisture-barrier backsheet stack for photovoltaic modules that provides reliable protection against moisture ingress over the long term to increase module lifetime. The stack includes an outer UV protective layer, an inner adhesion layer, barrier layers, and reinforcing layers. The barrier layers form a sealing layer between the UV and adhesion layers to block moisture diffusion. The reinforcing layers provide mechanical stability. The barrier layers prevent moisture gradients from forming, equalizing moisture levels across the stack over time.

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Photoelectric conversion element with improved sealing layers for high-temperature and high-humidity environments. The element comprises a photoelectric conversion layer, conductive layer, first sealing layer of inorganic metal oxide, nitride, oxynitride, or fluoride, and second sealing layer of polymer or nitride coating. The inorganic first sealing layer prevents oxygen and atomic oxygen penetration, while the second sealing layer provides additional protection against environmental degradation.

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A method for preparing solar cell modules with improved packaging performance, comprising: providing a substrate with a solar cell group and a sealant layer surrounding the group; creating an exhaust groove in the sealant layer; incorporating an air vent on the solar cell group; laminating the structure; heating the laminate while exhausting the sealant layer through the groove; and immediately laminating the structure after heating.

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A photovoltaic module with improved long-term reliability, comprising a transmissive front protective layer, a back protective layer, a plurality of solar cells, and a filler material that generates a free acid. The filler material is positioned between the front protective layer and the solar cells, and the front protective layer has microthrough-holes that allow moisture to reach the filler material while preventing water ingress into the module.

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The development of perovskite solar cells (PSCs) has ushered in a new era of solar technology, characterized by its exceptional efficiency and cost-effective production. However, the soft and fragile nature of perovskites makes module encapsulation challenging. Polyolefin elastomers (POEs) have been reported to be promising encapsulants for perovskite modules. However, little research exists on identifying criteria among different types of POEs as encapsulants. Here, two POEs with different morphologies were compared as encapsulants. The first POE crystallizes during encapsulation (crystal content 40%), and the resulting shrinkage or warpage leads to delamination, causing minimodule failure. In contrast, perovskite minimodules encapsulated with a mostly amorphous POE exhibited better reliability and reproducibility. The best perovskite minimodules passed the thermal cycling test for 240 cycles between 40 and 85 C and the damp heat test for 1419 h, according to the IEC 61215 standard. This study highlights the importance of the morphology of encapsulants in achieving high-quality e... Read More

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Abstract Perovskite solar cells promise to be part of the future portfolio of photovoltaic technologies, but their instability is slow down their commercialization. Major stability assessments have been recently achieved but reliable accelerated ageing tests on beyond small-area cells are still poor. Here, we report an industrial encapsulation process based on the lamination of highly viscoelastic semi-solid/highly viscous liquid adhesive atop the perovskite solar cells and modules. Our encapsulant reduces the thermomechanical stresses at the encapsulant/rear electrode interface. The addition of thermally conductive two-dimensional hexagonal boron nitride into the polymeric matrix improves the barrier and thermal management properties of the encapsulant. Without any edge sealant, encapsulated devices withstood multifaceted accelerated ageing tests, retaining >80% of their initial efficiency. Our encapsulation is applicable to the most established cell configurations (direct/inverted, mesoscopic/planar), even with temperature-sensitive materials, and extended to semi-transparent ce... Read More

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Abstract There is a significant deficiency in perovskite solar module (PSM) stability under thermomechanical stressors which is not well-understood. In this perspective, common issues seen with perovskite solar cell device fabrication related to thermomechanical reliability of PSM processing are discussed, with a focus on how the robustness of device layers and interlayer adhesion can be improved. Film stresses, adhesion of charge transport layers, and instability under light and heat are discussed with the purpose of providing insight on designing PSMs for durability. Processing conditions of encapsulation of PSMs and critical parameters to consider are also examined, and accelerated testing protocols for PSMs are discussed that probe mechanical degradation modes and ensure reliability of devices in the field.

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A solar cell with enhanced damp heat resistance, comprising a semiconductor substrate with a fine grid layer, a dielectric protection layer, and a busbar layer. The busbars penetrate through the dielectric protection layer and connect with the fine grids. The dielectric protection layer is formed between the fine grid layer and the busbar layer to prevent moisture and heat from reaching the fine grid layer, thereby enhancing the solar cell's resistance to damp heat aging.

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Abstract For commercial applications, Perovskite Solar Cells (PSCs) need to be well encapsulated to improve long term stability. The most common method, glass-glass encapsulation, uses edge sealant materials to encapsulate the device between sheets of glass. Glass-Glass encapsulation, while providing provide adequate protection from the ambient environment, limits the use of flexible substrates for thin film solar cells due to its rigidity. Additionally, the added weight of glass encapsulation reduces the specific power (W kg 1 ) of PSCs, which is an important factor when designing solar cells for aerospace applications. Here we demonstrate that commercially available acrylic spray encapsulation offers efficient and robust stability for PSCs. It is shown that applying the encapsulation via this method does not degrade the PSCs, unlike other literature and glass-glass encapsulation methods. Additionaly, it is shown that 1 coat of acrylic spray encapsulation has an effective thickness of 1.77 m and a weight of 6 mg. For stability measurements, PSCs with an acrylic coating show a 4... Read More

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Abstract 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 currentvoltage 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.

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A barrier assembly for photovoltaic devices comprising a barrier film and a polyurethane outer protective film layer bonded directly to the barrier film's exposed surface. The barrier film is a flexible, transparent layer comprising an inorganic oxide layer sandwiched between two polymer layers, while the polyurethane outer protective film layer provides additional protection against environmental factors such as UV radiation, moisture, and air infiltration. The assembly is suitable for protecting a wide range of photovoltaic devices, including organic photovoltaic devices, thin-film solar cells, perovskite solar cells, and dye-sensitized solar cells.

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Purpose Solar cells could make textile-based wearable systems energy independent without the need for battery replacement or recharging; however, their laundry resistance, which is prerequisite for the product acceptance of e-textiles, has been rarely examined. This paper aims to report a systematic study of the laundry durability of solar cells embedded in textiles. Design/methodology/approach This research included small commercial monocrystalline silicon solar cells which were encapsulated with functional synthetic textile materials using an industrially relevant textile lamination process and found them to reliably endure laundry washing (ISO 6330:2012). The energy harvesting capability of eight textile laminated solar cells was measured after 1050 cycles of laundry at 40 C and compared with light transmittance spectroscopy and visual inspection. Findings Five of the eight textile solar cell samples fully maintained their efficiency over the 50 laundry cycles, whereas the other three showed a 20%27% decrease. The cells did not cause any visual damage to the fabric. The result ... Read More

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The degradation behaviors of the encapsulant and the imbedded additives significantly determine the reliability of solar modules. Nevertheless, a link between the degradation of the encapsulant, including the additive interactions, and the longevity of the overall module is rarely established until now. Herein, minimodules containing ethylenevinyl acetate copolymer (EVA) as encapsulant are subject to damp heat (DH) or ultraviolet (UV) weathering based on IEC 61215. Macroscopically, the degradation under both weathering types characterized by I V measurements and electroluminescence (EL) measurements is diverging in dependence on the used stressor. Using electron paramagnetic resonance and orbitrap mass spectrometry, it is shown that deacetylation of the EVA occurs significantly for both types of weathering. In the case of DH, however, the mechanism of action of the UV stabilizer is hindered, so that strong encapsulant degradation is observed despite a lower energy input in comparison with UV. Furthermore, the produced acetic acid under DH weathering leads to the observed reductio... Read More

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The development of a reliable encapsulation is a key factor for protecting perovskite solar cells from extrinsic degradation and an important step to commercialization. The use of edge sealing materials has already been proven effective for rigid substrates. However, for flexible devices, a different encapsulation strategy must be developed. In this study, epoxy- and acrylic-based adhesives were tested over blade-coated p-i-n MAPI devices and the encapsulation was evaluated with currentvoltage measurements, calcium, and thermal stability tests. Although causing discoloration around the cells, over the area without the evaporated top electrode, the epoxy adhesive showed great performance after encapsulation and under thermal stress. This strategy was used to compare the stability of PEDOT:PSS and NiO as HTL. After an initial drop of 40 % in performance, the device with NiO was stable for over 5500 h under 85 C. These results show that this method can be used for evaluating the stability of perovskite solar cell and that, with further development of a proper buffer layer, epoxy-based... Read More

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Lightweight modules are essential for next-generation vehicle-integrated photovoltaic (VIPV) applications, such as solar-powered cars, allowing integration of solar cells beyond the roof, and on the hood, boot and body panels, and thereby extending the driving range. However, the lightweight module's reliability and corresponding degradation mechanisms under various environmental stresses are less researched. In this work, we investigate interconnection and encapsulation strategies to improve reliability against damp heat and mechanical impact. We fabricated lightweight mini modules, weighing around 3.45 kg/m2, and conducted hail impact and damp heat tests. These tests result in different failures, such as cracks in the solar cell, module delamination, and microcracks in the backsheet. By carrying out failure mechanism analysis and altering the fiber reinforcement in backsheet and encapsulation materials, we can increase resilience to these failure modes, thus providing guidance for the design of lightweight PV modules for next-generation VIPV.

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A bilayer polymer encapsulation strategy is used to improve the perovskite solar cells stability under high humidity conditions (80 5% RH).

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Enhancing the lifetime of perovskite solar cells (PSCs) is one of the essential challenges for their industrialization. Although the external encapsulation protects the perovskite device from the erosion of moisture and oxygen under various harsh conditions. However, the perovskite devices still undergo static and dynamic thermal stress during thermal and thermal cycling aging, respectively, resulting in irreversible damage to the morphology, component, and phase of stacked materials. Herein, the viscoelastic polymer polyvinyl butyral (PVB) material is designed onto the surface of perovskite films to form flexible interface encapsulation. After PVB interface encapsulation, the surface modulus of perovskite films decreases by nearly 50%, and the interface stress range under the dynamic temperature field (40 to 85 C) drops from 42.5 to 64.8 MPa to 14.8 to 5.0 MPa. Besides, PVB forms chemical interactions with FA + cations and Pb 2+ , and the macroscopic residual stress is regulated and defects are reduced of the PVB encapsulated perovskite film. As a result, the optimized device's ... Read More

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In the current work, we have employed an easy, simple, and cost-effective encapsulation process to enhance the lifespan of solar cells when exposed to challenging outdoor conditions. A solar cell was encapsulated using the liquid phase of a polyurethane elastomer prepared from low-cost vegetable castor oil, employing the simple and easy one-shot process with 2,4-toluene diisocyanate (TDI), and without the use of chain extenders. Optical transmission measurements revealed that the transparency of the encapsulant in the visible region reached 92 % with increasing TDI concentration, while the transparency was blocked in the ultraviolet (UV) region. Through the present work, the performance parameters of the solar cell have been enhanced after encapsulation with polyurethane under different compositions and thicknesses. The polyurethane encapsulant did not retain the applied temperature in the range of 30150 C, but rather transferred the heat outside the solar cell. We can conclude that the low-cost and easily prepared polyurethane is suitable for solar cell encapsulation in various en... Read More

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For the commercialization of perovskite solar cells (PSCs), detection of associated degradation mechanisms and mitigation of their effect is of paramount importance. The former requires outdoor and indoor stability tests to detect these mechanisms under real operation conditions and to accelerate them under controlled environments. Herein, the thermomechanical stability of encapsulated PSCs in outdoor tests at three locations coupled with indoor thermal cycling tests is investigated. Results show that encapsulantinduced partial delamination can occur in outdoor and indoor tests, leading to disruption in device integrity and substantial loss in the cell active area and shortcircuit current. The findings suggest that delamination involves C 60 and SnO 2 layers as the mechanically weakest point in the device stack. To the best of our knowledge, this work is the first demonstration of delamination in encapsulated PSCs under real operation conditions. While partial delamination emerged on some of the cells exposed in Israel and Cyprus in just a few weeks, it did not occur in Germany ove... Read More

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Abstract The delamination of encapsulants in photovoltaic (PV) modules is a common issue that leads to power loss due to optical losses. Encapsulant debonding is usually examined under monotonic loading conditions subsequent to environmental exposure such as damp heat. Servicerelevant, superimposed environmentalmechanical fatigue loads are not considered adequately. Hence, the environmental fatigue delamination resistance of thermally toughened double glass laminates with an ethylene vinyl acetate copolymer (EVA) adhesive layer was investigated in this study. Focus was given to the melting range of EVA, in which the noncrosslinked crystalline phase fraction is already in the partly molten state. Double cantilever beam specimens were tested on an electrodynamic test machine at temperatures of 60, 70, 80, and 90C and relative humidity (rh) levels of 2%, 30%, 50%, and 80%. The fractured surfaces were characterized by digital microscopy, Fourier transform infrared spectroscopy (FTIR), Xray photoelectron spectroscopy (XPS), and differential scanning calorimetry (DSC). The cyclic fati... Read More

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