Ultraviolet-induced Degradation Research Articles

Downshifting Encapsulant: Optical Simulation Evaluation of the Solution to Ultraviolet‐Induced Degradation in Silicon Heterojunction Solar Cells

Ultraviolet (UV)‐induced degradation (UVID) poses a significant challenge for the prospective mass production of silicon heterojunction (SHJ) solar cells, known for their high efficiency. In this study, the magnified impact of UV radiation when employing a silicon carbide (SiC)‐based transparent passivating contact (TPC) on the front side of SHJ solar cells is reported. A reduction in open‐circuit voltage (VOC), short‐circuit current (JSC), and fill factor of 12%, 6%, and 11%, respectively, is observed after UV exposure. Conventional UVID mitigation measures, UV‐blocking encapsulation, are assessed through single‐cell TPC laminates, revealing an unavoidable tradeoff between current loss and UVID. Alternatively, the utilization of ultraviolet‐downshifting (UV‐DS) encapsulants is proposed to convert UV radiation into the visible light spectrum. An optical simulation method, conducted via OPAL2, is presented to evaluate UV‐DS encapsulants for diminishing UVID in SHJ solar cells with different front contacts. A simple methodology is proposed to mimic the optical property of UV‐DS encapsulants. In the simulation results, additional current gains of up to 0.33 mA cm−2 achievable with suitable UV‐DS encapsulants are highlighted. The factors related to the UV‐DS effects are evaluated and the optimization pathway for UV‐DS encapsulants is elucidated.

Insights into mechanism of UV-induced degradation in silicon heterojunction solar cells

The ultraviolet-induced degradation (UVID), with losses of up to 11 % after 2000 h-exposure (Sinha et al., 2023) [1], impairs long-term stability of silicon heterojunction (SHJ) solar cells at present. However, the mechanism of UVID has remained only roughly understood till now. Herein, we shed light on the electrical properties of defects in SHJ solar cells to elucidate the underlying mechanism. Defect generation in SHJ solar cells after ultraviolet (UV) irradiation can be observed from photoluminescence (PL) images. Furthermore, we extract the density of states near Fermi level in hydrogenated amorphous silicon (a-Si:H) through analyzing carrier transport mechanism, and find the increment of state density induced by the UV irradiation. In conjunction with Fourier-transform infrared (FTIR) spectra, we ascribe the UV-induced defects to the rupture of Si–H and Si–H2 bonds. Besides, the intersection point between Fermi levels of the c-Si and a-Si:H/c-Si interface can be found shift toward valence band from admittance spectrum analysis, which is the cause of the higher interface state density based on the theory of Fermi energy dependent hydrogen diffusion energy. As a result, a potential mechanism of generation of recombination centers responsible for UVID in SHJ solar cells is proposed, which could provide insights into the possible solutions for UVID and enhance the long-term stability of SHJ solar cells.

Fabrication and Optimization of Pickering Emulsion Stabilized by Lignin Nanoparticles for Curcumin Encapsulation.

To develop reversible pH-responsive emulsifiers of natural origin, alkali lignin (AL) was used to develop oil-in-water Pickering emulsions. AL was first modified to synthesize quaternized alkali lignin (QAL), which displayed pH-responsive properties and demonstrated solubility in both acidic and alkaline solutions. In contrast, QAL exhibited insolubility and formed particles in neutral solutions, thereby making it a suitable candidate for utilization as an emulsifier in doubly pH-responsive Pickering emulsions. At pH 5-9, the emulsions were stable. Above or below this pH range, the system demulsifies, resulting in a reversible Pickering emulsifier with two pH-controlled transitions. On the basis of this pH-dependent behavior, lignin-based Pickering emulsions (LPE) could be subjected to several cycles of emulsification-demulsification by alternating the pH of the aqueous phase between basic and acidic, while the droplet size and storage stability were maintained. Curcumin was used as a drug model to study the loading/release behavior of LPE, finding that 50.08% of curcumin could be encapsulated in LPE. The in vitro release of curcumin was pH-dependent. In addition, LPE exhibited an outstanding protective effect against the ultraviolet-induced degradation of curcumin.

Spectroscopic probing of ultraviolet-induced degradation in elastomeric polyurea

Aromatic polyurea has garnered assiduous research due to its excellent impact, shock, abrasion, moisture, and chemical resistance properties. Polyurea can be used in protective coating and impact mitigation applications but is inevitably exposed to harsh deployment conditions such as extended ultraviolet (UV) radiation. Fourier Transform Infrared (FTIR) spectroscopy, Terahertz-time domain spectroscopy (THz-TDS), and Excitation-Emission Matrix spectroscopy (EEMS) deciphered the effects of UV radiation on radiated polyurea samples under ambient and nitrogen-rich conditions. Samples were radiated continuously for up to 15 weeks in increments of 3 weeks. Comprehensive FTIR analyses revealed a monotonic increase in disordered hydrogen bonding as a function of exposure duration in an ambient environment. Otherwise, marginal changes were observed in UV-radiated samples under nitrogen. The hydrogen bond length exhibited significant variations in the former compared to their nitrogen atmosphere counterparts. The results infer the nitrogen shielding effect, protecting polyurea from the photodegradation and photo-oxidation observed in samples radiated under the ambient atmosphere. THz-TDS spectra affirmed the FTIR results by probing changes in the complex refractive index. Terahertz spectral peaks associated with torsional vibrations of intermolecular hydrogen bonds in polyurea were notably correlated with increased exposure duration in the ambient atmosphere. Changes in the complex index as a function of exposure duration under nitrogen are minimal. The excitation-emission spectra of polyurea samples reveal a strong fluorescent behavior in 9-week and 12-week ambient-exposed polyurea due to cluster-triggered emission mechanisms. The results synthesized based on three different spectroscopy techniques paint a holistic portrait of the adverse effects of extended ultraviolet radiation of macromolecules deployed in harsh environmental conditions.

Fully Aromatic Self-Assembled Hole-Selective Layer toward Efficient Inverted Wide-Bandgap Perovskite Solar Cells with Ultraviolet Resistance.

Ultraviolet-induced degradation has emerged as a critical stability concern impeding the widespread adoption of perovskite solar cells (PSCs), particularly in the context of phase-unstable wide-band gap perovskite films. This study introduces a novel approach by employing a fully aromatic carbazole-based self-assembled monolayer, denoted as (4-(3,6-dimethoxy-9H-carbazol-9-yl)phenyl)phosphonic acid (MeO-PhPACz), as a hole-selective layer (HSL) in inverted wide-band gap PSCs. Incorporating a conjugated linker plays a pivotal role in promoting the formation of a dense and highly ordered HSL on substrates, facilitating subsequent perovskite interfacial interactions, and fostering the growth of uniform perovskite films. The high-quality film could effectively suppress interfacial non-radiative recombination, improving hole extraction/transport efficiency. Through these advancements, the optimized wide-band gap PSCs, featuring a band gap of 1.68 eV, attain an impressive power conversion efficiency (PCE) of 21.10 %. Remarkably, MeO-PhPACz demonstrates inherent UV resistance and heightened UV absorption capabilities, substantially improving UV resistance for the targeted PSCs. This characteristic holds significance for the feasibility of large-scale outdoor applications.

UV Light-Induced Degradation of Industrial Silicon HJT Solar Cells: Degradation Mechanism and Recovery Strategies

Abstract: The demand for Silicon heterojunction solar cells (HJT) has significantly grown recently. These solar cells have gained recognition for their remarkable performance, which can be attributed to the exceptional passivation properties of bilayers consisting of intrinsic and doped hydrogenated amorphous silicon. This study investigates alternative recovery methods and looks into the deterioration caused by UV radiation in commercial Silicon HJT solar cells. The carrier lifetimes of the samples were measured before and after the HJT solar cells were exposed to ultraviolet radiation. The findings revealed a decrease in carrier lifetime, iVoc, and iFF, indicating the creation of defects in the bulk of a-Si:H and the interface between c-Si and a-Si:H. It was assessed how SiOx performed as a passivation layer. It has been discovered that SiOx can passivate dangling bonds, increase carrier lifetime and reduce trap density. In addition, recovery techniques like current injection, infrared, light soaking, and annealing were applied. The current injection, infrared, and light soaking treatments were discovered to be able to partially restore the efficiency of the solar cells without the combination of temperature, while annealing was found to be more effective. Additionally, the effects of both short and prolonged exposure to UV are investigated. The HJT solar cells exposed to prolonged UV radiation for an extended period of time could not fully regain their efficiency and displayed irreparable flaws. Overall, this study demonstrates the potential of recovery treatments and passivation techniques in increasing the efficiency of Si HJT solar cells and illuminates the processes underlying ultraviolet-induced deterioration. Overall, this study sheds light on ultraviolet-induced degradation mechanisms and highlights the potential of recovery treatments and passivation techniques in enhancing the efficiency of Si HJT solar cells.

Accelerated UV stress testing and characterization of PV-modules: Reliability analysis using different encapsulants and glass sheets

Ethylene vinyl acetate (EVA) is the most commonly used encapsulant material in photovoltaic (PV) module fabrication. However, during long-term operation in the field under hot and dry climates, it turns yellow and finally brown due to action of ultraviolet (UV) light. Therefore, UV-light is a major concern causing photodegradation of encapsulant and significant loss in maximum power (Pmax) of PV-module. The main objective of this study is to provide deeper insights into degradation of electrical parameters in PV-modules under influence of UV-light and temperature, and minimize the impact of UV induced degradation (UVID) by replacing the encapsulant EVA with poly vinyl butyral (PVB). Four polycrystalline PV-modules, fabricated in different combinations from two types of encapsulants, namely PVB and EVA, and glass sheets, namely soda-lime and quartz, are subjected to an accelerated UV stress test for 350 h. Visual inspection, electroluminescence, infrared imaging, insulation resistance, wet leakage current, and maximum power determination tests were performed to characterize PV-modules intermittently throughout accelerated UV stress test. Based on obtained electrical parameters, PVB/soda-lime experienced the lowest 3% loss in Pmax, whereas EVA/quartz experienced the highest 7% loss in Pmax. In other two samples, EVA/soda-lime and PVB/quartz, Pmax reduced by 4% and 5% respectively.

Inverted planar heterojunction perovskite solar cells with high ultraviolet stability

Long-term stability remains a challenge for commercializing metal halide perovskites in photovoltaic (PV) applications. Ultraviolet-induced degradation (UV-ID) has been considered as one of the key stability issues for crystalline silicon PVs. However, limited studies have been performed on the long-term UV-ID of perovskite PVs, and none has been found related to operational stability under UV stressing. Here, we focus on UV-ID of inverted perovskite solar cells that comprise nickel oxide (NiO) as the hole transporting layer. Under continuous UV irradiation, we observe vacancies/voids generated in the vicinity of NiO/perovskite heterojunction. Time-resolved femtosecond transient absorption and double-ion injection current measurements indicate UV irradiation would induce interface shallow traps and severe ion migration. These UV-induced degradations can be greatly suppressed by modifying the heterojunction with a self-assembled monolayer [2-(9 H-Carbazol-9-yl)ethyl] phosphonic acid (2PACz). Unencapsulated NiO/2PACz devices, operated at maximum power point (MPP), retain over 90% of their initial efficiency after exposing to a total UV dose of 35 kWh/m2. The best-performing device reaches a stabilized efficiency of 22.2%, and retains 82% of its original efficiency after 2000 h of MPP tracking under one sun illumination (100 mW/cm2) at 45 ℃ in ambient air when encapsulated.

UV-induced degradation in multicrystalline PERC cell and module

The reliability of the long-term operation of multicrystalline silicon (mc-Si) modules is very important due to its large market share. However, mc-Si modules show significant degradation over time, when exposed to sunlight. In this paper, the changes in the electrical characteristics, before and after ultraviolet-induced degradation (UV-ID), were monitored in mc-Si passivated-emitter–rear-contact (PERC) cells. We first demonstrate that UV light causes the formation of defects in the bulk of solar cells, rather than destroying the surface passivation. An advanced hydrogen passivation process is performed to inhibit the bulk degradation and it is found that UV-ID is effectively suppressed on either the cell or the module.

CuCO3 and CuO nanoparticles; facile preparation and evaluation as photocatalysts

This work referred to the preparation of CuCO3 nanoparticles (NPs) with definite size and morphology via the simple, fast, cost effective, scale up able direct chemical precipitation method. Also, CuO NPs are prepared via solid state thermal decomposition of the carbonate precursor nano-material. In the first step of the two phase study, CuCO3 and CuO NPs were prepared through an easy approach and in a second step the photocatalytic properties of the two inorganic NPs were evaluated. The preparation of the NPs was performed through the optimized direct precipitation of the carbonate salt and its thermal decomposition to form the oxide NPs. The parameters influencing the properties of the carbonate particles through the direct precipitation method were optimized by the so-called Taguchi experiment design. The optimal CuCO3 NPs were next subjected to a thermal treatment step to form CuO NPs. The produced NPs were studied through X-ray diffraction, scanning electron microscopy, Fourier transform infra-red spectroscopy and thermogravimetry. Further the photocatalytic qualities of the carbonate and oxide NPs in the ultraviolet-induced degradation of methyl orange was monitored and both particles were found to be promising candidates for application in the reaction.

Surface Rutilization of Anatase TiO2 for Efficient Electron Extraction and Stable Pmax Output of Perovskite Solar Cells

Summary High-performance perovskite solar cells require efficient extraction of photogenerated electrons from the light absorber to the semiconductor skeleton, which can simultaneously stabilize the photovoltaic device by kinetically suppressing superoxide-intermediated degradation by reducing the accumulation of electrons in the perovskite layer. Here, we propose to improve and stabilize the photovoltaic performance of the cells by modulating the surface structures of TiO 2 . The transformed rutilized phase not only bridges the perovskite-TiO 2 interfacial charge transfer but also protects the light absorber from ultraviolet-induced degradation by suppressing the survival of holes generated in the TiO 2 skeleton. As a result of these merits, an increment of 50% in power conversion efficiency can be achieved. Furthermore, these cells exhibit extraordinary stability under continuous (120 hr) power-maximum output without cell encapsulation in the presence of moisture, oxygen, and ultraviolet irradiation and can restore to their initial photovoltaic performance by repeatedly undergoing tetragonal-to-cubic phase transition of the perovskite.

SCF(β-TRCP) promotes cell growth by targeting PR-Set7/Set8 for degradation.

The Set8/PR-Set7/KMT5a methyltransferase plays critical roles in governing transcriptional regulation, cell cycle progression and tumorigenesis. Although CRL4Cdt2 was reported to regulate Set8 stability, deleting the PIP motif only led to partial resistance to ultraviolet-induced degradation of Set8, indicating the existence of additional E3 ligase(s) controlling Set8 stability. Furthermore, it remains largely undefined how DNA damage-induced kinase cascades trigger the timely destruction of Set8 to govern tumorigenesis. Here, we report that SCFβ-TRCP earmarks Set8 for ubiquitination and degradation in a casein kinase I-dependent manner, which is activated by DNA-damaging agents. Biologically, both CRL4Cdt2 and SCFβ-TRCP-mediated pathways contribute to ultraviolet-induced Set8 degradation to control cell cycle progression, governing the onset of DNA damage-induced checkpoints. Therefore, like many critical cell cycle regulators including p21 and Cdt1, we uncover a tight regulatory network to accurately control Set8 abundance. Our studies further suggest that aberrancies in this delicate degradation pathway might contribute to aberrant elevation of Set8 in human tumours.

Photoprotective effect of starch/montmorillonite composites on ultraviolet-induced degradation of herbicides

Despite the extensive research about polymer/clay composites and nanocomposites, there have been few investigations devoted to the resistance of these hybrids against ultraviolet radiation. This property is especially of interest for materials based on biodegradable polymers since they could be applied for slow release of light-degradable molecules, such as herbicides. This paper describes the photoprotective effect of starch/montmorillonite composites on the ultraviolet-induced degradation of ametryne, a commercial herbicide. The starch/montmorillonite composites highly loaded with ametryne (50% by weight), and different contents of clay were produced by the starch gelatinization method. The results showed that encapsulation of ametryne by starch/montmorillonite composites is simple and possible to be done as a one-step procedure. It was shown that the main photodegradation mechanism involves herbicide volatilization, which was significantly reduced due to formation of composites with starch and montmorillonite. The composite presented a synergistic photoprotective effect between components. 13C solid-state nuclear magnetic resonance (13C-NMR) and FTIR spectroscopy indicated that the photoprotective effect is based on absorption of ultraviolet radiation by starch/montmorillonite composites, and not due to herbicide interaction with the hybrid structure. The novel composites for controlled or slow delivery of herbicides exhibited a promising efficiency in protecting active inputs against solar light degradation in field.

Synthesis of hyperbranched polyacetals via a n + b2 -type polyaddition (n = 3, 8, 18, and 21): Candidate resists for extreme ultraviolet lithography

Polyaddition (An + B2) reactions of 1,1,1-tris(4-hydoxyphenyl) ethane (THPE; A3-type monomer), calix[4]resorcinarene (CRA[4]; A8-type monomer), α-cyclodextrin (α-CD; A18-type monomer), and β-cyclodextrin (β-CD; A21-type monomer) with 1,4-bis(4-vinyloxy)cyclohexane (BVOC; B2-type monomer) afforded corresponding soluble hyperbranched polyacetals. The physical properties, including solubility, thermal stability, and film-forming ability, the ultraviolet-induced degradation reactivity, and the solubility-switch in an extreme ultraviolet (EUV) exposure tool indicated that poly(THPE-co-BVOC) and poly(CRA[4]-co-BVOC) are candidate next-generation photo-resists. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 2343–2350

UV-induced Degradation Study of Multicrystalline Silicon Solar Cells Made from Different Silicon Materials

The effect of ultraviolet-induced degradation (UV-ID) on solar cells made from two different solar grade materials has been compared. By using identical wafer and cell production units, effects originating in the two materials; solar grade produced by the Elkem Solar method (ESS™) was compared to standard polysilicon solar cells.Silicon wafers were selected precisely from similar positions from respective silicon bricks to process identical standard solar cells. The quantum efficiency maps at particular laser wavelengths and IV parameters of all solar cells were measured before and after UV-ID to visualize defects sites in the solar cells and to observe the extent of degradation. The experimental results indicate a general tendency that the cells made from the ESS™ material perform slightly better than standard polysilicon material.

Validated stability indicating liquid chromatographic determination of ebastine in pharmaceuticals after pre column derivatization: Application to tablets and content uniformity testing

An accurate, simple, sensitive and selective reversed phase liquid chromatographic method has been developed for the determination of ebastine in its pharmaceutical preparations. The proposed method depends on the complexation ability of the studied drug with Zn2+ ions. Reversed phase chromatography was conducted using an ODS C18 (150 × 4.6 mm id) stainless steel column at ambient temperature with UV-detection at 260 nm. A mobile phase containing 0.025%w/v Zn2+ in a mixture of (acetonitril/methanol; 1/4) and Britton Robinson buffer (65:35, v/v) adjusted to pH 4.2, has been used for the determination of ebastine at a flow rate of 1 ml/min. The calibration curve was rectilinear over the concentration range of 0.3 - 6.0 μg/ml with a detection limit (LOD) of 0.13 μg/ml, and quantification limit (LOQ) of 0.26 μg/ml. The proposed method was successfully applied for the analysis of ebastine in its dosage forms, the obtained results were favorably compared with those obtained by a comparison method. Furthermore, content uniformity testing of the studied pharmaceutical formulations was also conducted. The composition of the complex as well as its stability constant was also investigated. Moreover, the proposed method was found to be a stability indicating one and was utilized to investigate the kinetics of alkaline and ultraviolet induced degradation of the drug. The first-order rate constant and half life of the degradation products were calculated.

Ultraviolet-induced degradation of Ziegler-Natta and metallocene catalyzed polyethylenes

The metallocene revolution has aroused a storm of interest and associated questions regarding the performance and durability of polyolefins. This new technology has impacted the additives used to stabilize and process polymers. In this work, Ziegler-Natta and metallocene polyethylene (PE) samples were exposed to natural weather conditions under high doses of ultraviolet radiation, high temperature, and increased humidity. Weather-induced degradation of the two sets of PEs was studied using gel permeation chromatography, mechanical properties testing, differential scanning calorimetry, and Fourier transform infrared spectroscopy. The gel permeation chromatography analysis indicated the change in molecular weight distribution and molecular weights of metallocene PE to be more stable than conventional Ziegler-Natta PE. The tensile properties of metallocene PE are known to have higher values than Ziegler-Natta PE. The former exhibited a lower drop rate in mechanical properties when exposed to natural weather. Formations of nonvolatile carbonyl oxidation products, which absorb in the infrared region with a maximum absorbance level at 1742 cm−1 were determined. This indicated a higher rate of photo-oxidative and thermal degradation of Ziegler-Natta PE as compared with metallocene PE. The ultraviolet stabilization of metallocene PE may require different doses and a new kind of stabilizer system that can impart a longer useful lifetime and are cost effective for PE used for outdoor purposes. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1591–1596, 2000

The effect of caffeine on the repair of ultraviolet-damaged DNA in bacteria

1. 1. The effect of caffeine on host cell reactivation of ultraviolet-irradiated λ phage and on ultraviolet-induced degradation of bacterial DNA was investigated using an ultraviolet-sensitive and host cell reactivation negative mutant of Escherichia coli in which ultraviolet-induced DNA breakdown takes place. 2. 2. The photo-reactivation was rapidly impaired after infection of the mutant with ultraviolet-irradiated λ phage. In the presence of 1.0 % caffeine the photo-reactivatability of the ultraviolet-irradiated phage was almost completely preserved in this strain. 3. 3. Caffeine inhibited ultraviolet-induced DNA breakdown in bacteria. 4. 4. The intracellular state of the ultraviolet-irradiated λ phage DNA was studied using the sucrose density-gradient centrifugation technique, and it was observed that caffeine inhibited the introduction of a first clip in the λ phage DNA pre-exposed to ultraviolet light. 5. 5. It was suggested that caffeine depresses the excision of pyrimidine dimers from ultraviolet-irradiated DNA.

Abnormal metabolic response to ultraviolet light of a recombination deficient mutant of Escherichia coli K12

A given dose of ultraviolet irradiation produces as many pyrimidine-dimer-containing photoproducts in the DNA of the Escherichia coli Rec − strain JC1569 as it does in the related Rec + strain JC1557. Both strains excise dimer-containing photoproducts from their DNA to the same extent. In comparison with JC1557, approximately 30 times as much DNA of the Rec − strain is degraded per unit dose of ultraviolet light. Perhaps as a result of this excess ultraviolet-induced degradation, irradiated Rec − cells do not incorporate appreciable amounts of exogenous thymidine or thymine into DNA and have few survivors following exposure to an ultraviolet dose which almost all Rec + cells survive. A numerical argument is offered to establish the ability of Rec − cells successfully to replace excised pyrimidine-dimer-containing regions of the DNA with normal nucleotide residues. No effect of the rec − mutation in JC1569 was found on the level of activity of the following enzymes: endonuclease I, exonuclease I, exonuclease III and DNA phosphatase, and DNA polymerase and exonuclease II.