| 1. |
- Locke, Adam E, et al.
(författare)
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Genetic studies of body mass index yield new insights for obesity biology.
- 2015
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 518:7538, s. 197-401
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Tidskriftsartikel (refereegranskat)abstract
- Obesity is heritable and predisposes to many diseases. To understand the genetic basis of obesity better, here we conduct a genome-wide association study and Metabochip meta-analysis of body mass index (BMI), a measure commonly used to define obesity and assess adiposity, in up to 339,224 individuals. This analysis identifies 97 BMI-associated loci (P < 5 × 10(-8)), 56 of which are novel. Five loci demonstrate clear evidence of several independent association signals, and many loci have significant effects on other metabolic phenotypes. The 97 loci account for ∼2.7% of BMI variation, and genome-wide estimates suggest that common variation accounts for >20% of BMI variation. Pathway analyses provide strong support for a role of the central nervous system in obesity susceptibility and implicate new genes and pathways, including those related to synaptic function, glutamate signalling, insulin secretion/action, energy metabolism, lipid biology and adipogenesis.
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| 2. |
- Shungin, Dmitry, et al.
(författare)
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New genetic loci link adipose and insulin biology to body fat distribution.
- 2015
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 518:7538, s. 187-378
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Tidskriftsartikel (refereegranskat)abstract
- Body fat distribution is a heritable trait and a well-established predictor of adverse metabolic outcomes, independent of overall adiposity. To increase our understanding of the genetic basis of body fat distribution and its molecular links to cardiometabolic traits, here we conduct genome-wide association meta-analyses of traits related to waist and hip circumferences in up to 224,459 individuals. We identify 49 loci (33 new) associated with waist-to-hip ratio adjusted for body mass index (BMI), and an additional 19 loci newly associated with related waist and hip circumference measures (P < 5 × 10(-8)). In total, 20 of the 49 waist-to-hip ratio adjusted for BMI loci show significant sexual dimorphism, 19 of which display a stronger effect in women. The identified loci were enriched for genes expressed in adipose tissue and for putative regulatory elements in adipocytes. Pathway analyses implicated adipogenesis, angiogenesis, transcriptional regulation and insulin resistance as processes affecting fat distribution, providing insight into potential pathophysiological mechanisms.
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| 3. |
- Alberto, H. V., et al.
(författare)
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Slow-muon study of quaternary solar-cell materials : Single layers and p-n junctions
- 2018
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Ingår i: Physical Review Materials. - : AMER PHYSICAL SOC. - 2475-9953. ; 2:2
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Tidskriftsartikel (refereegranskat)abstract
- Thin films and p-n junctions for solar cells based on the absorber materials Cu(In, Ga) Se-2 and Cu2ZnSnS4 were investigated as a function of depth using implanted low energy muons. The most significant result is a clear decrease of the formation probability of the Mu(+) state at the heterojunction interface as well as at the surface of the Cu(In, Ga)Se-2 film. This reduction is attributed to a reduced bonding reaction of the muon in the absorber defect layer at its surface. In addition, the activation energies for the conversion from a muon in an atomiclike configuration to a anion-bound position are determined from temperature-dependence measurements. It is concluded that the muon probe provides a measurement of the effective surface defect layer width, both at the heterojunctions and at the films. The CIGS surface defect layer is crucial for solar-cell electrical performance and additional information can be used for further optimizations of the surface.
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| 4. |
- Bose, Sourav, et al.
(författare)
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A morphological and electronic study of ultrathin rear passivated Cu(In,Ga)Se2 solar cells
- 2019
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Ingår i: Thin Solid Films. - : Elsevier BV. - 0040-6090 .- 1879-2731. ; 671, s. 77-84
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Tidskriftsartikel (refereegranskat)abstract
- The effects of introducing a passivation layer at the rear of ultrathin Copper Indium Gallium di-Selenide Cu(In,Ga)Se2 (CIGS) solar cells is studied. Point contact structures have been created on 25 nm Al2O3 layer using e-beam lithography. Reference solar cells with ultrathin CIGS layers provide devices with average values of light to power conversion efficiency of 8.1% while for passivated cells values reached 9.5%. Electronic properties of passivated cells have been studied before, but the influence of growing the CIGS on Al2O3 with point contacts was still unknown from a structural and morphological point of view. Scanning Electron Microscopy, X-ray Diffraction and Raman spectroscopy measurements were performed. These measurements revealed no significant morphological or structural differences in the CIGS layer for the passivated samples compared with reference samples. These results are in agreement with the similar values of carrier density (~8 x 1016 cm-3) and depletion region (~160 nm) extracted using electrical measurements. A detailed comparison between both sample types in terms of current-voltage, external quantum efficiency and photoluminescence measurements show very different optoelectronic behaviour which is indicative of a successful passivation. SCAPS simulations are done to explain the observed results in view of passivation of the rear interface.
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| 5. |
- Cunha, J. M. V., et al.
(författare)
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Insulator Materials for Interface Passivation of Cu(In,Ga)Se-2 Thin Films
- 2018
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Ingår i: IEEE Journal of Photovoltaics. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 2156-3381 .- 2156-3403. ; 8:5, s. 1313-1319
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Tidskriftsartikel (refereegranskat)abstract
- In this work, metal-insulator-semiconductor structures were fabricated in order to study different types of insulators, namely, aluminum oxide (Al2O3), silicon nitride, and silicon oxide (SiOx) to be used as passivation layers in Cu(In,Ga)Se-2 (CIGS) thin-film solar cells. The investigated stacks consisted of SLG/Mo/CIGS/insulator/Al. Raman scattering and photoluminescence measurements were done to verify the insulator deposition influence on the CIGS surface. In order to study the electrical properties of the CIGS-insulator interface, capacitance versus conductance and voltage (C-G-V) measurements were done to estimate the number and polarity of fixed insulator charges (Q(f)). The density of interface defects (D-it) was estimated from capacitance versus conductance and frequency (C-G-f) measurements. This study evidences that the deposition of the insulators at high temperatures (300 degrees C) and the use of a sputtering technique cause surface modification on the CIGS surface. We found that, by varying the SiOx deposition parameters, it is possible to have opposite charges inside the insulator, which would allow its use in different device architectures. The material with lower Dit values was Al2O3 when deposited by sputtering.
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| 6. |
- Curado, M. A., et al.
(författare)
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Front passivation of Cu(In,Ga)Se-2 solar cells using Al2O3 : Culprits and benefits
- 2020
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Ingår i: APPLIED MATERIALS TODAY. - : ELSEVIER. - 2352-9407. ; 21
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Tidskriftsartikel (refereegranskat)abstract
- In the past years, the strategies used to break the Cu(In,Ga)Se-2 (CIGS) light to power conversion efficiency world record value were based on improvements of the absorber optoelectronic and crystalline properties, mainly using complex post-deposition treatments. To reach even higher efficiency values, further advances in the solar cell architecture are needed, in particular, with respect to the CIGS interfaces. In this study, we evaluate the structural, morphological and optoelectronic impact of an Al2O3 layer as a potential front passivation layer on the CIGS properties, as well as an Al2O3 tunneling layer between CIGS and CdS. Morphological and structural analyses reveal that the use of Al2O3 alone is not detrimental to CIGS, although it does not resist to the CdS chemical bath deposition. The CIGS optoelectronic properties degrade when the CdS is deposited on top of Al2O3. Nonetheless, when Al2O3 is used alone, the optoelectronic measurements reveal a positive impact of this inclusion such as a very low concentration of interface defects while keeping the same CIGS recombination channels. Thus, we suggest that an Al2O3 front passivation layer can be successfully used with alternative buffer layers. Depth-resolved microscopic analysis of the CIGS interface with slow-muons strongly suggests for the first time that low-energy muon spin spectroscopy (LE-mu SR) is sensitive to both charge carrier separation and bulk recombination in complex semiconductors. The demonstration that Al2O3 has the potential to be used as a front passivation layer is of significant importance, considering that Al2O3 has been widely studied as rear interface passivation material. (C) 2020 Published by Elsevier Ltd.
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| 7. |
- Fernandes, P. A., et al.
(författare)
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Phase selective growth of Cu12Sb4S13 and Cu3SbS4 thin films by chalcogenization of simultaneous sputtered metal precursors
- 2019
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Ingår i: Journal of Alloys and Compounds. - : Elsevier BV. - 0925-8388 .- 1873-4669. ; 797, s. 1359-1366
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Tidskriftsartikel (refereegranskat)abstract
- In this work, we present a procedure to grow Cu12Sb4S13 and Cu3SbS4 thin films consisting of the deposition of simultaneously sputtered metal precursors followed by a annealing treatment in a sulphur atmosphere. The selection of the ternary phase is performed by adjusting the sulphur evaporation temperature in the chalcogenization process. It is shown that for a sulphur evaporation temperature of 140 °C the predominant phase is Cu12Sb4S13 while for 180 °C the predominant phase is Cu3SbS4. In order to ensure precursor composition homogeneity, the Cu-Sb metallic precursors are deposited simultaneously by RF magnetron sputtering using adjustable segmented targets. The morphological characterization of the films was made by scanning electron microscopy and the composition was analysed by energy dispersive spectroscopy. The structural analysis and phase identification were performed by X-ray diffraction and Raman scattering. The optical properties were studied on films deposited directly on bare glass and the optical bandgap energies of 1.47 eV and 0.89 eV for Cu12Sb4S13 and Cu3SbS4, respectively, were determined.
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| 8. |
- Lopes, T. S., et al.
(författare)
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Cu(In,Ga)Se2 based ultrathin solar cells the pathway from lab rigid to large scale flexible technology
- 2023
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Ingår i: npj Flexible Electronics. - : Springer Nature. - 2397-4621. ; 7:1
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Tidskriftsartikel (refereegranskat)abstract
- The incorporation of interface passivation structures in ultrathin Cu(In,Ga)Se2 based solar cells is shown. The fabrication used an industry scalable lithography technique—nanoimprint lithography (NIL)—for a 15 × 15 cm2 dielectric layer patterning. Devices with a NIL nanopatterned dielectric layer are benchmarked against electron-beam lithography (EBL) patterning, using rigid substrates. The NIL patterned device shows similar performance to the EBL patterned device.The impact of the lithographic processes in the rigid solar cells’ performance were evaluated via X-ray Photoelectron Spectroscopy and through a Solar Cell Capacitance Simulator. The device on stainless-steel showed a slightly lower performance than the rigid approach, due to additional challenges of processing steel substrates, even though scanning transmission electron microscopy did not show clear evidence of impurity diffusion. Notwithstanding, time-resolved photoluminescence results strongly suggested elemental diffusion from the flexible substrate. Nevertheless, bending tests on the stainless-steel device demonstrated the mechanical stability of the CIGS-based device.
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| 9. |
- Alberto, H. V., et al.
(författare)
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Low energy muon study of the p-n interface in chalcopyrite solar cells
- 2023
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Ingår i: Journal of Physics, Conference Series. - : Institute of Physics Publishing (IOPP). - 1742-6588 .- 1742-6596. ; 2462
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Tidskriftsartikel (refereegranskat)abstract
- The slow muon technique was used to study the p-n junction of chalcopyrite solar cells. A defect layer near the interface was identified and the passivation of the defects by buffer layers was studied. Several cover layers on top of the chalcopyrite Cu(In,Ga)Se2 (CIGS) semiconductor absorber were investigated in this work, namely CdS, ZnSnO, Al2O3 and SiO2. Quantitative results were obtained: The defect layer extends about 50 nm into the CIGS absorber, the relevant disturbance is strain in the lattice, and CdS provides the best passivation, oxides have a minor effect. In the present contribution, specific aspects of the low-energy muon technique in connection with this research are discussed.
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| 10. |
- Ben Sedrine, N., et al.
(författare)
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Fluctuating potentials in GaAs : Si nanowires: Critical reduction of the influence of polytypism on the electronic structure
- 2018
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Ingår i: Nanoscale. - : Royal Society of Chemistry (RSC). - 2040-3364 .- 2040-3372. ; 10:8, s. 3697-3708
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Tidskriftsartikel (refereegranskat)abstract
- In this work, the effects of Si doping in GaAs nanowires (NWs) grown on GaAs (111)B by molecular beam epitaxy with different Si doping levels (nominal free carrier concentrations of 1 × 1016, 8 × 1016, 1 × 1018 and 5 × 1018 cm-3) are deeply investigated using scanning electron microscopy (SEM), transmission electron microscopy (TEM), grazing incidence X-ray diffraction (GID), photoluminescence (PL) and cathadoluminescence (CL). TEM results reveal a mixture of wurtzite (WZ) and zinc-blende (ZB) segments along the NW axis independently of the Si doping levels. GID measurements suggest a slight increase of the ZB fraction with the Si doping. Low temperature PL and CL spectra exhibit sharp lines in the energy range 1.41-1.48 eV, for the samples with lower Si doping levels. However, the emission intensity increases and is accompanied by a clear broadening of the observed lines for the samples with higher Si doping levels. The staggered type-II band alignment only determines the optical properties of the lower doping levels in GaAs:Si NWs. For the higher Si doping levels, the electronic energy level structure of the NWs is determined by electrostatic fluctuating potentials intimately related to the amphoteric behavior of the Si dopant in GaAs. For the heavily doped NWs, the estimated depth of the potential wells is ∼96-117 meV. Our results reveal that the occurrence of the fluctuating potentials is not dependent on the crystalline phase and shows that the limitation imposed by the polytypism can be overcome.
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