Band alignment of Sb2O3 and Sb2Se3

Antimony selenide (Sb2Se3) possesses great potential in the field of photovoltaics (PV) due to its suitable properties for use as a solar absorber and good prospects for scalability. Previous studies have reported the growth of a native antimony oxide (Sb2O3) layer at the surface of Sb2Se3 thin films during deposition and exposure to air, which can affect the contact between Sb2Se3 and subsequent layers. In this study, photoemission techniques were utilized on both Sb2Se3 bulk crystals and thin films to investigate the band alignment between Sb2Se3 and the Sb2O3 layer. By subtracting the valence band spectrum of an in situ cleaved Sb2Se3 bulk crystal from that of the atmospherically contaminated bulk crystal, a valence band offset (VBO) of −1.72 eV is measured between Sb2Se3 and Sb2O3. This result is supported by a −1.90 eV VBO measured between Sb2O3 and Sb2Se3 thin films via the Kraut method. Both results indicate a straddling alignment that would oppose carrier extraction through the back contact of superstrate PV devices. This work yields greater insight into the band alignment of Sb2O3 at the surface of Sb2Se3 films, which is crucial for improving the performance of these PV devices

The last trip of the baby boomers: life and Death of Public Space in the cinema in the 1960s and 1970s

[Resumen] La generación nacida al final de la II Guerra Mundial llegó a su juventud arrastrada por la inercia del optimismo tecnocrático que había desarrollado la generación anterior. En un contexto de bonanza económica, la juventud se rebeló contra el sistema generando una nueva sensibilidad que daría lugar a diferentes respuestas contraculturales. En estos intentos de cambiar la sociedad, las ciudades asistieron a una recodificación de los espacios públicos. El espacio urbano, desacreditado bajo los ecos de “la muerte de la calle” promulgada por Le Corbusier, se reactivó como escenario de protesta y acción. Sin embargo, este resurgir de lo público se diluyó rápidamente al compás del desencanto juvenil. Una vez confirmada la imposibilidad de transformar el sistema, se produjo una búsqueda de otros territorios que el cine interpretó bajo dos estrategias: por un lado, la producción de espacios urbanos totalmente inhóspitos y desolados; por otro lado, un repliegue hacia lo individual reflejado en nuevas formas de habitar. Pequeñas comunidades, comunas y la vuelta a una vida rural controlada serán respuestas que, lejos de construir un ámbito público, resultarán finalmente el argumento que estaba buscando el sistema para la destrucción y reconfiguración del dominio público. El cine de finales de los años sesenta y principios de los setenta muestra el desencanto del final de un deseo que acaba identificándose con una iconografía de la destrucción, desamparo y vacío.[Abstract] The generation of those who were born at the end of the Second World War reached their youth carried by the inertia of the technocratic optimism developed by the previous generation. In a context of economic bonanza, the younger generation rebelled against the system, creating a new sensibility which would spawn different countercultural responses. Within these attempts to change society, cities witnessed a re-codification of public spaces. Urban space, discredited by the echoes of the ‘death of the street’ promoted by Le Corbusier, was reactivated as a stage for protest and action. However, this revival of public space was rapidly suffocated by the disenchantment of the youth. Once the impossibility to transform the system had been confirmed, a search for new territories started, which cinema interpreted following two strategies: on the one hand, through the production of definitely inhospitable and devastated urban spaces; on the other, by retreating to the individual sphere, which reflected on new modes of habitation. Small communities, communes, and the return to a controlled rural life would be responses which, far from building public realms, would ultimately provide the system with the argument it was looking for in order to destroy and reconfigure the public domain. The films of the late 1960s and early 1970s show the ultimate disenchantment of a desire that, in the end, was attached to an iconography of destruction, abandonment, and emptiness

Evolution of multiple domains of the HIV-1 envelope glycoprotein during coreceptor switch with CCR5 antagonist therapy

HIV-1 uses CD4 as a receptor and chemokine receptors CCR5 and/or CXCR4 as coreceptors. CCR5 antagonists are a class of antiretrovirals used to inhibit viral entry. Phenotypic prediction algorithms such as Geno2Pheno are used to assess CCR5 antagonist eligibility, for which the V3 region is screened. However, there exist scenarios where the algorithm cannot give an accurate prediction of tropism. The current study examined coreceptor shift of HIV-1 from CCR5-tropic strains to CXCR4-tropic or dual-tropic strains among five subjects in a clinical trial of the CCR5 antagonist vicriviroc. Envelope gene amplicon libraries were constructed and subjected to next-generation sequencing, as well as single-clone sequencing and functional analyses. Approximately half of the amplified full-length single envelope-encoding clones had no significant activity for infection of cells expressing high levels of CD4 and CCR5 or CXCR4. Functional analysis of 9 to 21 individual infectious clones at baseline and at the time of VF were used to construct phylogenetic trees and sequence alignments. These studies confirmed that specific residues and the overall charge of the V3 loop were the major determinants of coreceptor use, in addition to specific residues in other domains of the envelope protein in V1/V2, V4, C3, and C4 domains that may be important for coreceptor shift. These results provide greater insight into the viral genetic determinants of coreceptor shift

Multi-Phase Sputtered TiO2-Induced Current–Voltage Distortion in Sb2Se3 Solar Cells

Despite the recent success of CdS/Sb2Se3 heterojunction devices, cadmium toxicity, parasitic absorption from the relatively narrow CdS band gap (2.4 eV) and multiple reports of inter-diffusion at the interface forming Cd(S,Se) and Sb2(S,Se)3 phases, present significant limitations to this device architecture. Among the options for alternative partner layers in antimony chalcogenide solar cells, the wide band gap, non-toxic titanium dioxide (TiO2) has demonstrated the most promise. It is generally accepted that the anatase phase of the polymorphic TiO2 is preferred, although there is currently an absence of analysis with regard to phase influence on device performance. This work reports approaches to distinguish between TiO2 phases using both surface and bulk characterization methods. A device fabricated with a radio frequency (RF) magnetron sputtered rutile-TiO2 window layer (FTO/TiO2/Sb2Se3/P3HT/Au) achieved an efficiency of 6.88% and near-record short–circuit current density (Jsc) of 32.44 mA cm−2, which is comparable to established solution based TiO2 fabrication methods that produced a highly anatase-TiO2 partner layer and a 6.91% efficiency device. The sputtered method introduces reproducibility challenges via the enhancement of interfacial charge barriers in multi-phase TiO2 films with a rutile surface and anatase bulk. This is shown to introduce severe S-shaped current–voltage (J–V) distortion and a drastic fill–factor (FF reduction in these devices

Growth and Characterization of Sb2Se3 Single Crystals for Fundamental Studies

Three methods of growing bulk crystalline samples of Sb2 Se3 to provide material for basic studies have been investigated and preliminary racterization is reported. These growth methods were: A) melt-growth, similar to vertical Bridgman, b) dynamic vapor transport over a temperature gradient (Piper-Polich method) and c) a static vapor method in which the source material is transported in nearly iso-thermal conditions. The melt-growth method produced the largest single crystals (up to 4 mm diameter), while the vapor methods both yielded polycrystalline boules with mm-sized grains. Powder XRD confirmed the boules to comprise orthorhombic Sb2 Se3, having lattice parameters a = 11.7808 Å b = 3.9767 Å and c = 11.6311 Å. Cleavage facets were parallel to (100). Raman peaks at 191 (A g and 211 cm -1 were excited anisotropically. FTIR reflectance features showed some sensitivity to s- and ppolarization

CSS Antimony Selenide Film Morphology and High Efficiency PV Devices

Knowledge of close-space sublimation (CSS) Sb 2 Se 3 growth conditions is vital for proper understanding of PV performance, and optimization of Sb 2 Se 3 devices. In this work, various growth parameters have been studied and the resulting Sb 2 Se 3 films have been characterized using SEM, XRD and optical transmission measurements, thus illustrating the desired properties for high device performance. PV devices were fabricated using TiO 2 as a window layer combined with P3HT or PTB7 as the hole transport material, resulting in V oc =0.42 V, J sc =33.4 mAcm -2 , FF = 43.2% and PCE = 6.06% for P3HT

Interface-Engineered Ni-Coated CdTe Heterojunction Photocathode for Enhanced Photoelectrochemical Hydrogen Evolution.

Photoelectrochemical (PEC) water splitting for hydrogen production using the CdTe photocathode has attracted much interest due to its excellent sunlight absorption property and energy band structure. This work presents a study of engineered interfacial energetics of CdTe photocathodes by deposition of CdS, TiO2, and Ni layers. A heterostructure CdTe/CdS/TiO2/Ni photocathode was fabricated by depositing a 100-nm n-type CdS layer on a p-type CdTe surface, with 50 nm TiO2 as a protective layer and a 10 nm Ni layer as a co-catalyst. The CdTe/CdS/TiO2/Ni photocathode exhibits a high photocurrent density (Jph) of 8.16 mA/cm2 at 0 V versus reversible hydrogen electrode (VRHE) and a positive-shifted onset potential (Eonset) of 0.70 VRHE for PEC hydrogen evolution under 100 mW/cm2 AM1.5G illumination. We further demonstrate that the CdTe/CdS p-n junction promotes the separation of photogenerated carriers, the TiO2 layer protects the electrode from corrosion, and the Ni catalyst improves the charge transfer across the electrode/electrolyte interface. This work provides new insights for designing noble metal-free photocathodes toward solar hydrogen development

Band gap temperature-dependence of close-space sublimation grown Sb2Se3 by photo-reflectance

The candidate photovoltaic absorber antimony selenide Sb2Se3 has been prepared by the commercially attractive close-space sublimation method. Structure, composition, and morphology are studied by x-ray diffraction, scanning electron microscopy, and energy dispersive spectroscopy. Large rhubarb-like grains favorable for photovoltaics naturally develop. The temperature-dependence of the direct band gap is determined by photoreflectance between 20 and 320 K and is well described by the Varshni and Bose–Einstein relations, blue-shifting with decreasing temperature from 1.18 to 1.32 eV. The 300 K band gap matches that seen in high quality single-crystal material, while the 0 K gap is consistent with that found in first-principles calculations, further supporting the array of beneficial photovoltaic properties indicated for this material

The Homeric and Hesiodic conception of the universe

Abstract taken from the Introduction section of the thesis: The chief purpose of this paper is to give a full account of the Homeric and Hesiodic ideas of the different parts of the universe, the main sources of information being the Iliad and Odyssey of Homer, the Theogony of Hesiod, the Homeric hymns, and Apollodorus

A post deposition annealing approach for organic residue control in TiO2 and its impact on Sb2Se3 TiO2 device performance

We report a systematic investigation on the influence of two step post deposition treatments PDTs on TiO2 buffer layers deposited by ultrasonic spray pyrolysis USP for emerging Sb2Se3 photovoltaics. Air annealing is a typical method for recrystallizing chemically deposited TiO2 films. However, organic residues such as carbon species from a precursor solution based on titanium tetraisopropoxide and acetylacetone may still remain on the TiO2 surface, therefore requiring an additional annealing step. We demonstrate that vacuum annealing can be a suitable technological approach to decrease the concentration of carbon species in TiO2 films. Vacuum annealing was performed at temperatures at 160 450 C prior to the 450 C air annealing step. It was found that vacuum annealing at 160 C followed by subsequent air annealing led to better device performance. This was explained by achieving an optimal balance between the removal of carbon content during vacuum annealing and the active recrystallization of TiO2 during air annealing. The decrease of carbon concentration by employing the two step approach was supported by changes in the lattice parameters of TiO2 and proven by X ray photoelectron spectroscopy XPS . The given study provides experimental evidence on how nanoscale carbon species in the TiO2 heterojunction partner layer of a Sb2Se3 solar cell can affect the device s performance. By this approach, we generate complementary insights on how the quality of the main interface has an impact and can take a key role despite the optimized Sb2Se3 grain structure and orientatio