A Comprehensive Study of Intermetallic Compounds in Solar Cell Interconnections and their Growth Kinetics

AbstractIntermetallic compounds (IMC) in soldered interconnections influence the reliability of PV modules. Thus, the microstructure of solar cell interconnections and the growth of IMCs are to be investigated in this paper. Sn60Pb40 and Sn41Bi57Ag2 are chosen as alloy coatings of copper interconnectors and semi-automatically soldered to screen-printed front Ag-busbars of industrial mono-crystalline solar cells. The microstructure of the solder bonds is characterized with metallographic cross sections and confocal laser microscopy, as well as scanning electron microscopy and electron dispersive x-ray spectroscopy. The cross section samples are isothermally aged between 85°C to 150°C and for 15 hour to 155 hour to obtain the kinetic parameters of a diffusion-based growth model of the IMCs. The model is used to estimate the IMC thickness after 3000h at 85°C, and after 600 thermal cycles as well as after 25 years in the outdoor location Freiburg, Germany. It is found that extensive microstructural changes take place within the solder bonds during thermal aging. Grain coarsening within the solder matrix, in particular for Sn41Bi57Ag2 solders, is observed, which can lead to an entire Sn depletion of the solder matrix. Moreover, non-uniform Sn penetration and IMC growth at cavities and lead-glass particles of the busbar are observed for both solders, which is discussed in terms of its effect on metallization adhesion. Eventually, simulating the IMC growth for 3000h at 85°C forecasts a 3.7μm thick Ag3Sn IMC at the busbar for the Sn41Bi57Ag2 solder compared to 2.6μm for Sn60Pb40. The prognosis of the IMC thickness after 25 years in Freiburg yields an Ag3Sn thickness of 1.3μm for Sn41Bi57Ag2

A Comprehensive Study of Module Layouts for Silicon Solar Cells Under Partial Shading

Integrated applications for solar energy production becomes increasingly important. The electrification of car bodies and building facades are only two prominent examples. In such applications shading becomes a challenging problem, since the classic serial interconnection of solar cells in terms of power output is highly vulnerable to partial shading. In this article, we investigate the three most common module layouts in the market (conventional, butterfly, and shingle string) and add a fourth layout (shingle matrix) to be introduced to the market in the future. We discuss an approach to cluster shadings occurring in urban surroundings into basic shapes like “rectangular” and “random”. Choosing a Monte Carlo technique in combination with latin hypercube sampling (LHS), we consider more than 3000 scenarios in total. For the evaluation of the scenarios, we conduct circuit simulations using LTspice. Furthermore, we define a normalization base, which considers only partial shading as a quantitative baseline for comparison. Our results show, that already for 200–400 scenarios the obtained output values stabilize. Among the investigated module layouts, the shingle matrix interconnection achieves the highest score, followed by a shingle string, half-cell butterfly and the conventional full-cell layout

Framework and baseline examination of the German National Cohort (NAKO)

The German National Cohort (NAKO) is a multidisciplinary, population-based prospective cohort study that aims to investigate the causes of widespread diseases, identify risk factors and improve early detection and prevention of disease. Specifically, NAKO is designed to identify novel and better characterize established risk and protection factors for the development of cardiovascular diseases, cancer, diabetes, neurodegenerative and psychiatric diseases, musculoskeletal diseases, respiratory and infectious diseases in a random sample of the general population. Between 2014 and 2019, a total of 205,415 men and women aged 19–74 years were recruited and examined in 18 study centres in Germany. The baseline assessment included a face-to-face interview, self-administered questionnaires and a wide range of biomedical examinations. Biomaterials were collected from all participants including serum, EDTA plasma, buffy coats, RNA and erythrocytes, urine, saliva, nasal swabs and stool. In 56,971 participants, an intensified examination programme was implemented. Whole-body 3T magnetic resonance imaging was performed in 30,861 participants on dedicated scanners. NAKO collects follow-up information on incident diseases through a combination of active follow-up using self-report via written questionnaires at 2–3 year intervals and passive follow-up via record linkages. All study participants are invited for re-examinations at the study centres in 4–5 year intervals. Thereby, longitudinal information on changes in risk factor profiles and in vascular, cardiac, metabolic, neurocognitive, pulmonary and sensory function is collected. NAKO is a major resource for population-based epidemiology to identify new and tailored strategies for early detection, prediction, prevention and treatment of major diseases for the next 30 years. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s10654-022-00890-5

Natural Products as Anti-HIV Agents and Role in HIV-Associated Neurocognitive Disorders (HAND): A Brief Overview

As the threat of Human Immunodeficiency Virus (HIV)/Acquired Immunodeficiency Syndrome (AIDS) persists to rise, effective drug treatments are required to treat the infected people. Even though combination antiretroviral therapy (cART) provides stable viral suppression, it is not devoid of undesirable side effects, especially in persons undergoing long-term treatment. The present therapy finds its limitations in the emergence of multidrug resistance and accordingly finding new drugs and novel targets is the need of the hour to treat the infected persons and further to attack HIV reservoirs in the body like brain, lymph nodes to achieve the ultimate goal of complete eradication of HIV and AIDS. Natural products such as plant-originated compounds and plant extracts have enormous potential to become drug leads with anti-HIV and neuroprotective activity. Accordingly, many research groups are exploring the biodiversity of the plant kingdom to find new and better anti-HIV drugs with novel mechanisms of action and for HIV-associated neurocognitive disorders (HAND). The basic challenge that still persists is to develop viral replication-targeted therapy using novel anti-HIV compounds with new mode of action, accepted toxicity and less resistance profile. Against this backdrop, the World Health Organization (WHO) suggested the need to evaluate ethno-medicines for the management of HIV/AIDS. Consequently, there is need to evaluate traditional medicine, particularly medicinal plants and other natural products that may yield effective and affordable therapeutic agents. Although there are a good number of reports on traditional uses of plants to treat various diseases, knowledge of herbal remedies used to manage HIV/AIDS and HAND are scanty, vague and not well documented. In this review, plant substances showing a promising action that is anti-HIV and HAND will be explored along with what they interact. Since some plant substances are also known to modulate several cellular factors which are also involved in the replication of HIV and hence their role as potential candidates will be discussed. HIV/AIDS being an exceptional epidemic, demands an exceptional approach and that forms very much focus for the current review

Effectiveness and safety of opicapone in Parkinson’s disease patients with motor fluctuations: the OPTIPARK open-label study

Background The efficacy and safety of opicapone, a once-daily catechol-O-methyltransferase inhibitor, have been established in two large randomized, placebo-controlled, multinational pivotal trials. Still, clinical evidence from routine practice is needed to complement the data from the pivotal trials. Methods OPTIPARK (NCT02847442) was a prospective, open-label, single-arm trial conducted in Germany and the UK under clinical practice conditions. Patients with Parkinson’s disease and motor fluctuations were treated with opicapone 50 mg for 3 (Germany) or 6 (UK) months in addition to their current levodopa and other antiparkinsonian treatments. The primary endpoint was the Clinician’s Global Impression of Change (CGI-C) after 3 months. Secondary assessments included Patient Global Impressions of Change (PGI-C), the Unified Parkinson’s Disease Rating Scale (UPDRS), Parkinson’s Disease Questionnaire (PDQ-8), and the Non-Motor Symptoms Scale (NMSS). Safety assessments included evaluation of treatment-emergent adverse events (TEAEs) and serious adverse events (SAEs). Results Of the 506 patients enrolled, 495 (97.8%) took at least one dose of opicapone. Of these, 393 (79.4%) patients completed 3 months of treatment. Overall, 71.3 and 76.9% of patients experienced any improvement on CGI-C and PGI-C after 3 months, respectively (full analysis set). At 6 months, for UK subgroup only (n = 95), 85.3% of patients were judged by investigators as improved since commencing treatment. UPDRS scores at 3 months showed statistically significant improvements in activities of daily living during OFF (mean ± SD change from baseline: − 3.0 ± 4.6, p < 0.0001) and motor scores during ON (− 4.6 ± 8.1, p < 0.0001). The mean ± SD improvements of − 3.4 ± 12.8 points for PDQ-8 and -6.8 ± 19.7 points for NMSS were statistically significant versus baseline (both p < 0.0001). Most of TEAEs (94.8% of events) were of mild or moderate intensity. TEAEs considered to be at least possibly related to opicapone were reported for 45.1% of patients, with dyskinesia (11.5%) and dry mouth (6.5%) being the most frequently reported. Serious TEAEs considered at least possibly related to opicapone were reported for 1.4% of patients. Conclusions Opicapone 50 mg was effective and generally well-tolerated in PD patients with motor fluctuations treated in clinical practice. Trial registration Registered in July 2016 at clinicaltrials.gov (NCT02847442)

Lead-free Solders for Ribbon Interconnection of Crystalline Silicon PERC Solar Cells with Infrared Soldering

We report about the analysis of Pb-free, low-temperature solders for the ribbon-interconnection of PERC solar cells with an industrial infrared stringer. Five solders (SnPb, SnBi-A, SnBi-B, SnBiAg and a proprietary lead-free, low-temperature (PLFLT) alloy) are characterized with differential scanning calorimetry to determine the melting and solidification temperature. It is found that SnBi-B, SnBiAg, and the PLFLT composition melt in a temperature range between 137 C to 171 C instead of a single temperature. Solidification occurs at a 3K to 11K lower temperature (undercooling). Mono-crystalline silicon PERC cells are contacted using an industrial stringer. The microstructure of the solder bonds is investigated with scanning electron microscopy. For the SnBi-A-solder, large and brittle Bi-phases are identified. The SnBi-B, SnBiAg and PLFLT solder show a finer grain structure. The added Ag in SnBiAg forms an intermetallic compound of Ag3Sn close to the Cu-core of the ribbon. The peel strength of the connected solar cells with the Pb-free solders is on average 1Nmm\u1000001 or slightly higher. Some bonds show low adhesion. The observed fracture mode is mainly failure at the busbar metallization to solar cell irrespective of the solder type. However, the occasionally observed solder residues on the metallization clearly reveal brittle fracture for the Pb-free solders, which is not observed for SnPb. First reliability tests show similar degradation of 1% to 2% for all solders