The Role of Surfaces, Interfaces and Oxides in Antimony Selenide Photovoltaics

This thesis investigates antimony selenide (Sb2Se3) as an absorber layer for photovoltaic cells. Literature focus thus far has centred around orientation and device optimisation. Fundamental material bulk, surface and interface properties are explored here as well as integration of Sb2Se3 layers into solar cell devices. The phonon modes of Sb2Se3 are investigated by standard, and angle-resolved polarised Raman spectroscopy to resolve inconsistencies in the Raman literature of the material. Oriented bulk crystals of Sb2Se3 are used and a stringent peak-fitting procedure employed to deconvolute individual vibrational modes in the spectra. Group theory calculations predicted the intensity variation of Raman peaks with rotation of the samples and these are fitted to the experimentally observed variations to assign vibrational symmetries to each mode. The results are corroborated by density functional theory calculations and previous literature reports. 14 of the 30 predicted phonon modes are experimentally observed and assigned vibrational symmetries. An x-ray photoelectron spectroscopy study of Sb2Se3 samples directly after fabrication, stored under atmospheric conditions or in vacuum is reported in order to understand spontaneous device improvements shortly after fabrication. Highly surface localised oxidation of the films stored in air as well as the formation of a more selenium-rich back surface is shown to improve the back contact, possibly by decreasing recombination at the interface and resulting in a 10% increase in efficiency of the cells over time. These results are experimentally verified by the deposition of thin layers of selenium and/or Sb2O3 at the back contact. Finally, a device study is presented with molybdenum-doped indium oxide (IMO) trialled as a partner layer for Sb2Se3 solar cells. The properties of sputtered IMO films are found to depend on the history of the sputtering target which is very sensitive to oxygen exposure. The IMO-Sb2Se3 interface is also found to be non-ideal for carrier collection but further studies may be able to overcome this challenge. Alternative deposition methods are suggested for future work but promising initial efficiencies of 0.57% were achieved

Plano de marketing : estudo de caso da empresa Eikon Soluções em Sinalização Ltda

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Mussel-Inspired Self-Healing Coatings Based on Polydopamine-Coated Nanocontainers for Corrosion Protection

The mussel-inspired properties of dopamine have attracted immense scientific interest for surface modification of nanoparticles due to the high potential of dopamine functional groups to increase the adhesion of nanoparticles to flat surfaces. Here, we report for the first time a novel type of inhibitor-loaded nanocontainer using polydopamine (PDA) as a pH-sensitive gatekeeper for mesoporous silica nanoparticles (MSNs). The encapsulated inhibitor (benzotriazole) was loaded into MSNs at neutral pH, demonstrating fast release in an acidic environment. The self-healing effect of water-borne alkyd coatings doped with nanocontainers was achieved by both on-demand release of benzotriazole during the corrosion process and formation of the complexes between the dopamine functional groups and iron oxides, thus providing dual self-healing protection for the mild steel substrate. The coatings were characterized by electrochemical impedance spectroscopy, visual observations, and confocal Raman microscopy. In all cases, the coatings with embedded benzotriazole-loaded MSNs with PDA-decorated outer surfaces demonstrated superior self-healing effects on the damaged areas. We anticipate that dopamine-based multifunctional gatekeepers can find application potential not only in intelligent self-healing anticorrosive coatings but also in drug delivery, antimicrobial protection, and other fields

Identifying Raman Modes of Sb2Se3 and their Symmetries using Angle-Resolved Polarised Raman Spectra

The physical properties of antimony selenide (Sb2Se3) are highly anisotropic. Angle-resolved polarised Raman spectroscopy was employed to characterise oriented crystals and used in conjunction with group theory structural analysis to assign vibrational symmetries to the peaks observed in the Raman spectra. The phonon energies were corroborated via density functional theory (DFT) calculations. Furthermore, a straightforward method is proposed to verify the desirable (001) plane orientation of film growth for device applications via minimisation of the 155 cm−1 peak in the Raman spectrum

TMEM16A and TMEM16B modulate pheromone-evoked action potential firing in mouse vomeronasal sensory neurons

The mouse vomeronasal system controls several social behaviors. Pheromones and other social cues are detected by sensory neurons in the vomeronasal organ (VNO). Stimuli activate a transduction cascade that leads to membrane potential depolarization, increase in cytosolic Ca2+ level, and increased firing. The Ca2+-activated chloride channels TMEM16A and TMEM16B are co-expressed within microvilli of vomeronasal neurons, but their physiological role remains elusive. Here, we investigate the contribution of each of these channels to vomeronasal neuron firing activity by comparing wild-type (WT) and knock-out (KO) mice. Performing loosepatch recordings from neurons in acute VNO slices, we show that spontaneous activity is modified by Tmem16a KO, indicating that TMEM16A, but not TMEM16B, is active under basal conditions. Upon exposure to diluted urine, a rich source of mouse pheromones, we observe significant changes in activity. Vomeronasal sensory neurons (VSNs) from Tmem16a cKO and Tmem16b KO mice show shorter interspike intervals (ISIs) compared with WT mice, indicating that both TMEM16A and TMEM16B modulate the firing pattern of pheromone-evoked activity in VSNs

Transition metal speciation as a degradation mechanism with the formation of a solid-electrolyte interphase (SEI) in Ni-rich transition metal oxide cathodes

An ever-growing demand for high-energy density and high-power Li-ion batteries has driven active research for electrode materials with superior capacity. Recent years have seen the development of Ni-rich transition metal oxide cathode materials due to their high reversible capacity and lower cost. To achieve full capacity from the charge compensation process, a high voltage (>4.4 V) charging is required. However, the battery operation at higher voltages eventually results in dramatic capacity fading and voltage decay with a rapid decomposition of the electrolyte upon further charge-discharge. While previous studies have reported the degradation mechanism within the electrode surface, there have been few empirical investigations into the solid-electrolyte interphase (SEI) formation on Ni-rich cathodes. In the current work, we visualize the different nature of the electrode-electrolyte interphase at various cut-off voltages (2.0-4.2 V, 2.0-4.5 V, and 2.0-4.8 V). We correlate the key properties of the SEI layer with the capacity fading mechanism in the high capacity battery system. The speciation of transition metal elements (Ni, Mn, and Co) into various oxidation and spin states has been identified as the dominant process of the capacity degradation

Vegard Relation and Raman Band Reference Data Generated from Bulk Crystals of Kesterite-Phase Composition Series Cu2ZnSnS4xSe4–4x (CZTSSe, 0 ≤ x ≤ 1)

Solid solutions in the series Cu2ZnSnS4xSe4–4x (CZTSSe) are of interest for PV applications. The purpose of this work was to grow bulk crystalline samples over the entire composition range to allow the Vegard relation (lattice parameter variation with composition) and the systematic behavior of Raman bands to be defined to generate reference data. Samples with 0 ≤ x ≤ 1 were synthesized from the elements and grown into crystalline form from solution in either KCl/NaCl eutectic or elemental Sn. Details of the crystal growth outcomes, including the use of a quartz seed plate to make thick film samples, are described. Ordered kesterite-type material was formed upon crystallization, and X-ray diffraction demonstrated linear Vegard relationships, with the lattice parameters varying with composition as a (Å) = −0.268(3)x + 5.6949(17) and c (Å) = −0.516(6)x + 11.345(3). Raman spectroscopy yielded two dominant peaks, these being kesterite A modes associated with the Se and S modes in CZTSe and CZTS. These varied in wavenumber linearly as ωCZTSe (cm–1) = (44.6 ± 1.6)x + (194.6 ± 0.8) and ωCZTS (cm–1) = (7.1 ± 1.3)x + (329.0 ± 0.8). Crystallization was also shown to promote ordering. The variation of lattice parameters with composition exhibited significant differences from those observed in previous studies. Also, while the Raman S mode behavior differed from previous reports, the Se modes were similar. These differences are discussed

Sn 5 s 2 lone pairs and the electronic structure of tin sulphides: A photoreflectance, high-energy photoemission, and theoretical investigation

The effects of Sn 5 s lone pairs in the different phases of Sn sulphides are investigated with photoreflectance, hard x-ray photoemission spectroscopy (HAXPES), and density functional theory. Due to the photon energy-dependence of the photoionization cross sections, at high photon energy, the Sn 5 s orbital photoemission has increased intensity relative to that from other orbitals. This enables the Sn 5 s state contribution at the top of the valence band in the different Sn-sulphides, SnS, Sn 2 S 3 , and SnS 2 , to be clearly identified. SnS and Sn 2 S 3 contain Sn(II) cations and the corresponding Sn 5 s lone pairs are at the valence band maximum (VBM), leading to ∼ 1.0 –1.3 eV band gaps and relatively high VBM on an absolute energy scale. In contrast, SnS 2 only contains Sn(IV) cations, no filled lone pairs, and therefore has a ∼ 2.3 eV room-temperature band gap and much lower VBM compared with SnS and Sn 2 S 3 . The direct band gaps of these materials at 20 K are found using photoreflectance to be 1.36, 1.08, and 2.47 eV for SnS, Sn 2 S 3 , and SnS 2 , respectively, which further highlights the effect of having the lone-pair states at the VBM. As well as elucidating the role of the Sn 5 s lone pairs in determining the band gaps and band alignments of the family of Sn-sulphide compounds, this also highlights how HAXPES is an ideal method for probing the lone-pair contribution to the density of states of the emerging class of materials with n s 2 configuration

TRIIAL national reports Belgium, Hungary, Italy, Poland, Portugal, Romania, Slovenia, Spain, The Netherlands

Recent constitutional and legislative changes in several member states are questioning core features of EU rule of law. For the first time ever, the EU institutions have proposed activation of the preventive mechanism in Article 7 TEU against Poland and Hungary, and the European Commission has launched the rule of law conditionality mechanism against Hungary. The jurisprudence of the CJEU finding numerous violations of judicial independence and fundamental rights undermining the rule of law in Europe is growing at a fast pace. Moreover, many preliminary references show the willingness of national courts to engage in judicial dialogue with the CJEU, relying on it to provide harmonised standards and guidelines on the rule of law. However, the future of such interactions is undermined by recent decisions of supreme and constitutional courts limiting the rights of domestic courts to use the preliminary reference procedure and prohibiting their obligation to give effect to EU law based on a tendentious understanding of national constitutional identity. In this context, the TRIIAL project has embarked on an ambitious research quest, which resulted in the present Edited Working Paper. It consists of nine country reports which cover the most relevant issues concerning judicial independence, impartiality, accountability, mutual trust and the rule of law in the jurisdictions of the project partners: Belgium, the Netherlands, Hungary, Romania, Italy, Portugal, Poland, Spain and Slovenia. The country reports primarily build on case law identified and analysed during the TRIIAL project and published in the CJC database. They outline the current state of affairs and challenges the member states face in the topics covered by TRIIAL exposing and analysing specific pressing issues, especially ones that are not yet covered in other reports such as the European Commission’s Rule of Law report.