Development of CIGS2 Thin Films on Ultralightweight Flexible Large Area Foil Sunstrates

The development of thin film solar cells is aimed at reducing the costs for photovoltaic systems. Use of thin film technology and thin foil substrate such as 5-mil thick stainless steel foil or 1-mil thick Ti would result in considerable costs savings. Another important aspect is manufacturing cost. Current single crystal technology for space power can cost more than $300 per watt at the array level and weigh more than 1 kg/sq m equivalent to specific power of approx. 65 W/kg. Thin film material such as CuIn1-xGaxS2 (CIGS2), CuIn(1-x)Ga(x)Se(2-y)S(y) (CIGSS) or amorphous hydrogenated silicon (a-Si:H) may be able to reduce both the cost and mass per unit area by an order of magnitude. Manufacturing costs for solar arrays are an important consideration for total spacecraft budget. For a medium sized 5kW satellite for example, the array manufacturing cost alone may exceed$ 2 million. Moving to thin film technology could reduce this expense to less than $ 500K. Earlier publications have demonstrated the potential of achieving higher efficiencies from CIGSS thin film solar cells on 5-mil thick stainless steel foil as well as initial stages of facility augmentation for depositing thin film solar cells on larger (6 in x 4 in) substrates. This paper presents the developmental study of achieving stress free Mo coating; uniform coatings of Mo back contact and metallic precursors. The paper also presents the development of sol gel process, refurbishment of selenization/sulfurization furnace, chemical bath deposition (CBD) for n-type CdS and scrubber for detoxification of H2S and H2Se gases

Dissecting the Shared Genetic Architecture of Suicide Attempt, Psychiatric Disorders, and Known Risk Factors

Background Suicide is a leading cause of death worldwide, and nonfatal suicide attempts, which occur far more frequently, are a major source of disability and social and economic burden. Both have substantial genetic etiology, which is partially shared and partially distinct from that of related psychiatric disorders. Methods We conducted a genome-wide association study (GWAS) of 29,782 suicide attempt (SA) cases and 519,961 controls in the International Suicide Genetics Consortium (ISGC). The GWAS of SA was conditioned on psychiatric disorders using GWAS summary statistics via multitrait-based conditional and joint analysis, to remove genetic effects on SA mediated by psychiatric disorders. We investigated the shared and divergent genetic architectures of SA, psychiatric disorders, and other known risk factors. Results Two loci reached genome-wide significance for SA: the major histocompatibility complex and an intergenic locus on chromosome 7, the latter of which remained associated with SA after conditioning on psychiatric disorders and replicated in an independent cohort from the Million Veteran Program. This locus has been implicated in risk-taking behavior, smoking, and insomnia. SA showed strong genetic correlation with psychiatric disorders, particularly major depression, and also with smoking, pain, risk-taking behavior, sleep disturbances, lower educational attainment, reproductive traits, lower socioeconomic status, and poorer general health. After conditioning on psychiatric disorders, the genetic correlations between SA and psychiatric disorders decreased, whereas those with nonpsychiatric traits remained largely unchanged. Conclusions Our results identify a risk locus that contributes more strongly to SA than other phenotypes and suggest a shared underlying biology between SA and known risk factors that is not mediated by psychiatric disorders.Peer reviewe

Cigs2 Thin Films On Large Area Ultralightweight Ti/Sio2 Substrates

High efficiency solar cells on ultralightweight Ti substrates can be utilized for novel terrestrial and space applications. Large-area sputtering systems and selenization/sulfurization facility have been constructed and installed for development of large (15 cm × 10 cm) CIGS2 thin-film solar cells for terrestrial and space applications. The primary focus of this research was to fabricate thin film solar cells on insulating, ultralightweight SiO 2 coated Ti foil substrate to increase its specific power for space applications. Leveling capability of sol-gel SiO2 layers onto titanium foil substrate was analyzed by atomic force microscopy and profilometer roughness measurements. Results of planarization of Ti foil substrates using SiO2 coating, sputtering system design upgrade and thickness uniformity of thin films deposited over large area by DC and RF magnetron sputtering sources are presented

Predicting thermal runaway in bypass diodes in photovoltaic modules

Bypass diodes in photovoltaic (PV) modules can undergo thermal runaway while transitioning from forward bias state to reverse bias. Theoretical framework has been developed for predicting the susceptibility of bypass diodes to thermal runaway. The operating temperature of diode in forward bias is dependent on thermal resistance of diode-junction box system and the forward current through the diode. A new parameter -\u27critical temperature\u27 (junction temperature at which forward power dissipation in diode equals reverse power dissipation for given forward current and reverse voltage) is introduced. Critical temperature is only dependent on the forward current through the diode and reverse voltage that would get applied to the diode in reverse bias. Critical temperature is shown to be independent of external factors such as thermal resistance of diode/junction box and ambient temperature. It is shown that the diode undergoes thermal runaway while transitioning from forward bias to reverse bias only if the operating diode junction temperature is greater than the critical temperature. Based on this understanding, a model is developed to predict vulnerability of various Schottky bypass diodes for thermal runaway as a function of thermal resistance and forward current. The results are experimentally verified using a specially developed setup for thermal runaway testing of bypass diodes

Predicting Thermal Runaway In Bypass Diodes In Photovoltaic Modules

Bypass diodes in photovoltaic (PV) modules can undergo thermal runaway while transitioning from forward bias state to reverse bias. Theoretical framework has been developed for predicting the susceptibility of bypass diodes to thermal runaway. The operating temperature of diode in forward bias is dependent on thermal resistance of diode-junction box system and the forward current through the diode. A new parameter -\u27critical temperature\u27 (junction temperature at which forward power dissipation in diode equals reverse power dissipation for given forward current and reverse voltage) is introduced. Critical temperature is only dependent on the forward current through the diode and reverse voltage that would get applied to the diode in reverse bias. Critical temperature is shown to be independent of external factors such as thermal resistance of diode/junction box and ambient temperature. It is shown that the diode undergoes thermal runaway while transitioning from forward bias to reverse bias only if the operating diode junction temperature is greater than the critical temperature. Based on this understanding, a model is developed to predict vulnerability of various Schottky bypass diodes for thermal runaway as a function of thermal resistance and forward current. The results are experimentally verified using a specially developed setup for thermal runaway testing of bypass diodes

Revising The Bypass Diode Test To Incorporate The Effects Of Photovoltaic Module Mounting Configuration And Climate Of Deployment

Bypass diodes provide protection to Photovoltaic (PV) modules against partial shading. The existing qualification test for bypass diodes within the International Electrotechnical Commission (IEC) 61215 standard, entitled \u27Bypass Diode Test\u27 (BPDT), does not take into account the differences in end use environments experienced by PV modules due to different climates of deployments and mounting configurations. The current test is shown to be inadequate for climates/mounting configurations that result in high temperature end use environments for PV modules. A thermal model for bypass diode temperature in field was developed and applied to modules deployed in 16 representative climatic zones and two mounting configurations (rack mount and roof mount). A revised test condition was developed by varying the forward current through diodes and module temperature to minimize the false positive and false negative errors

Development Of Cigs2 Thin Film Solar Cells

Research and development of CuIn1-xGaxSe 2-ySy (CIGSS) thin-film solar cells on ultralightweight flexible metallic foil substrates is being carried out at FSEC PV Materials Lab for space applications. Earlier, the substrate size was limited to 3 cm × 2.5 cm. Large-area sputtering systems and scrubber for hydrogen selenide and sulfide have been designed and constructed for preparation of CIGSS thin-films on large (15 cm × 10 cm) substrates. A selenization/sulfurization furnace donated by Shell (formerly Siemens) Solar has also been refurbished and upgraded. The sputtering target assembly design was modified for proper clamping of targets and effective cooling. A new design of the magnetic assembly for large-area magnetron sputtering sources was implemented so as to achieve uniform deposition on large area. Lightweight stainless steel foil and ultralightweight titanium foil substrates were utilized to increase the specific power of solar cells. Sol-gel derived SiO2 layers were coated on titanium foil by dip coating method. Deposition parameters for the preparation of molybdenum back contact layers were optimized so as to minimize the residual stress as well as reaction with H2S. Presently large (15 cm × 10 cm) CuIn 1-xGaxS2 (CIGS2) thin film solar cells are being prepared on Mo-coated titanium and stainless steel foil by sulfurization of CuGa/In metallic precursors in diluted Ar:H2S(4%). Heterojunction partner CdS layers are deposited by chemical bath deposition. The regeneration sequence of ZnO/ZnO:Al targets was optimized for obtaining consistently good-quality, transparent and conducting ZnO/ZnO:Al bilayer by RF magnetron-sputter deposition. Excellent facilities at FSEC PV Materials Lab are one of its kinds and could serve as a nucleus of a small pilot plant for CIGSS thin film solar cell fabrication. © 2004 Elsevier B.V. All rights reserved

Development Of Sputtering Systems For Large-Area Deposition Of Cuin1-XGaXSe1-YSY Thin-Film Solar Cells

Optimum magnetic field distribution was obtained empirically by selectively removing nickel-coated soft iron pieces at the rear of the magnetron sputtering sources. In turn, the distribution resulted in a thickness uniformity of ±3% over central 10.2 cm length for molybdenum thin films. A completely modified magnetic array in which the magnetic field at the extremities was boosted by introducing strong magnets at and near the periphery, resulting in thickness uniformity for molybdenum of ±2.24% over 10.2 cm, ±2.4% over 12.7 cm, and ±2.95% over 15.2 cm; and zinc oxide, ±2.46% over 10.2 cm, ±3.84% over 12.7 cm, and ±5.6% over 15.2 cm