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The electronic properties of nine solid phosphorus (P)containing compounds with varying oxidation states and chemical environments, including GaP(‑III), InP(‑III), red-P(0), H3P(III)O3, Na2H2P2(IV)O6, H3P(V)O4, KH2P(V)O4, Na2HP(V)O4, and InP(V)O4, are investigated using X-ray absorption near-edge structure (XANES) spectroscopy in the hard (P K-edge) and soft X-ray regime (P L2,3edge). We find shifts in the absorption-edge positions and correlate them with the ligands surrounding the P atom, likely causing a different core−hole interaction screening for different compounds. Complementing the experimental analysis, ab initio many-body calculations of XANES spectra provide insights into the excitonic nature of the observed spectral features and their impact on the electronic structure of the materials. Furthermore, we report on P K-edge XANES measurements on aqueous phosphorus-containing acids, including H3PO3, H3PO4, and their mixtures. At first sight, the spectra of the aqueous acids are similar to those of their solid counterparts. However, close inspection reveals a slight red shift of the absorption edge and the presence of fewer spectral features compared with spectra of the respective solids. Mixtures of aqueous acids display spectral features corresponding to the individual components, indicating the potential for speciation and quantification through fingerprinting (Figure Presented).

Simultaneously enhancing device performance and longevity, as well as balancing the requirements on cost, scalability, and simplification of processing, is the goal of interface engineering of organic solar cells (OSCs). In our work, we strategically introduce antimony (Sb3+) cations into an efficient and generic n-type SnO2 nanoparticles (NPs) host during the scalable flame spray pyrolysis synthesis. Accordingly, a significant switch of conduction property from an n-type character to a p-type character is observed, with a corresponding shift in the work function (WF) from 4.01 ± 0.02 eV for pristine SnO2 NPs to 5.28 ± 0.02 eV for SnO2 NPs with 20 mol. % Sb content (ATO). Both pristine SnO2 and ATO NPs with fine-tuned optoelectronic properties exhibit remarkable charge carrier extraction properties, excellent UV resistance and photo-stability being compatible with various state-of-the-art OSCs systems. The reliable and scalable pristine SnO2 and ATO NPs processed by doctor-blading in air demand no complex post-treatment. Our work offers a simple but unique approach to accelerate the development of advanced interfacial materials, which could circumvent the major existing interfacial problems in solution-processed OSCs.

The chemical and electronic structures in the near-surface region of Cu(In,Ga)Se2 thin-film solar cell absorbers are investigated using nondestructive soft and hard X-ray photoelectron spectroscopy. In addition to a pronounced surface Cu-depletion, the [Ga]/([In]+[Ga]) composition indicates that the topmost surface is Ga-poor (or In-rich). For the studied depth region, common depth profiling techniques generally fail to provide reliable information and, thus, the near-surface chemical and electronic structure profiles are often overlooked. The relation between the observed near-surface elemental compositions and the derived electronic properties of the absorber material is discussed. It is found that the surface band gap energy crucially depends on the Cu-deficiency of the absorber surface and suggests that it is, in this region, only secondarily determined by the [Ga]/([In]+[Ga]) ratio.

Performance‐enhancing heavy alkali‐based post‐deposition treatments (PDT) of Cu(In,Ga)Se2 (CIGSe) thin‐film solar cells absorbers often induce the formation of a Rb‐ In‐Se phase on the CIGSe absorber. Co‐evaporation of an interfacial RbInSe2 (RISe) layer between buffer and absorber can also benefit cell performance. A detailed analysis of the chemical interface structures in CdS/RISe/CIGSe layer stacks is performed using hard X‐ray photoelectron spectroscopy (HAXPES). For comparison, stacks without RISe and based on RbF PDT CIGSe absorbers are also studied. When aiming for the direct co‐evaporation of a RISe layer on the CIGSe absorber, the formation of an additional In‐Se phase is found. For the RbF PDT CIGSe absorbers, the study only finds small amounts of Rb and no indication for a RISe layer formation. Examining layer stacks prepared via additional chemical bath deposition (CBD) of CdS reveals a clear impact of the presence of Rb (or of Rb‐containing species) on the CIGSe surface. In these cases, an increase of the induction/coalescence period is found at the beginning of the CBD buffer layer growth process and the formation of Cd─Se bonds; thereafter, a more compact CdS layer growth is observed. [ABSTRACT FROM AUTHOR]

Sputter‐deposited GaOx (i.e., oxygen‐deficient gallium oxide) films are evaluated as a potential replacement for the standard CdS buffer layers in Cu(In,Ga)Se2 (CIGSe) based thin‐film photovoltaics. The energy level alignment at the GaOx/CIGSe and CdS/CIGSe interfaces are compared by means of direct and inverse photoemission. For the GaOx/CIGSe a (0.04 ± 0.07) eV (i.e., a small spike‐like) conduction band offset (CBO) and a (−3.21 ± 0.19) eV (i.e., a large cliff‐like) valence band offset (VBO) are found, which suggests a nearly ideal charge‐selective contact. The derived GaOx band gap of (4.80 ± 0.25) eV confirms its utility as a highly transparent buffer layer. However, the GaOx (with x derived to be 1.1 ± 0.1) exhibits considerable (presumably) defect‐related occupied states above the valence band maximum. It is proposed that these states may increase charge carrier recombination and decrease open circuit voltage in respective devices; also explaining why solar cells with standard CdS buffer outperform devices with GaOx buffer, despite less ideal electronic interface properties (CBO: (−0.18 ± 0.07) eV, VBO: (−0.98 ± 0.15) eV) and the smaller CdS band gap of (2.35 ± 0.22) eV. [ABSTRACT FROM AUTHOR]

The development of freestanding and binder‐free electrode is an effective approach to perform the inherent capacity of active materials and promote the mechanism study by minimizing the interference from additives. Herein, we construct a freestanding cathode composed of MoS3/PPy nanowires (NWs) deposited on porous nickel foam (NF) (MoS3/PPy/NF) through electrochemical methods, which can work efficiently as sulfur‐equivalent cathode material for Li‐S batteries. The structural stability of the MoS3/PPy/NF cathode is greatly enhanced due to its significant tolerance to the volume expansion of MoS3 during the lithiation process, which we ascribe to the flexible 3D framework of PPy NWs, leading to superior cycling performance compared to the bulk‐MoS3/NF reference. Eliminating the interference of binder and carbon additives, the evolution of the chemical and electronic structure of Mo and S species during the discharge/charge was studied by X‐ray absorption near‐edge spectroscopy (XANES). The formation of lithium polysulfides was excluded as the driving cathode reaction mechanism, suggesting the great potential of MoS3 as a promising sulfur‐equivalent cathode material to evade the shuttle effect for Li‐S batteries. The present study successfully demonstrates the importance of structural design of freestanding electrode enhancing the cycling performances and revealing the corresponding mechanisms. [ABSTRACT FROM AUTHOR]

The layered structure of van der Waals compounds enables facile insertion of guest species between layers, resulting in material multifunctionality through easily modifying its physical properties. Isostructural MPS3 compounds with 3d transition metal cations such as Mn, Fe, Co and Ni can serve as hosts for relatively small alkali metals as well as larger organic molecules. NiPS3 is the most exotic representative among them, because despite 30 years of intense research, its electronic structure still evokes numerous questions, not to mention the electronic structure of intercalated NiPS3. There are two possibilities for electron transfer in semiconducting NiPS3 upon insertion of electron-donating species, either to a discrete Ni atomic level, or to a molecular level of the (P2S6)4− unit. We performed a systematic structural and spectroscopic study of NiPS3 upon electrochemical intercalation of Li, Na and 1-ethyl-3-methylimidazolium (EMIM) cations. Up to 0.5 Li or 0.5 Na per NiPS3 formula unit can be inserted into free octahedral spaces in the interlayers without visible changes in the diffraction pattern of the host. In contrast, more than 1 EMIM per NiPS3 unit can be intercalated between host layers leading to a significant interlayer distance expansion from 6.33 Å to 11.3 Å. The charge compensation was found to be different for the three intercalants: upon Li insertion, the electron density increases on the (P2S6)4− unit and Ni remains redox-inactive, while intercalation of Na leads to reduction of Ni. In contrast, uptake of larger EMIM cations does not result in any changes in Ni, S and P K-edge near edge XANES spectra of NiPS3 and results in only very little change in their extended X-ray absorption fine structure spectra. It is likely that there is an electrochemical reduction of EMIM cations to heterocyclic carbenes with their possible dimerization. The impact on magnetization of Li and EMIM intercalation was also studied. [ABSTRACT FROM AUTHOR]

Durante la última década se incrementó la superficie agrícola, que incluyó el uso de suelos poco aptos y su consecuente degradación en la Región Semiárida Pampeana. Los cultivos de cobertura son una herramienta que puede minimizar tal degradación y compensar el balance de carbono. Nuestro objetivo fue evaluar el efecto de tres momentos de quemado de un cultivo de cobertura (CC) como el centeno, sobre el aporte de biomasa del CC, el contenido hídrico y el nitrato del suelo, la presencia de malezas en el cultivo sucesor y rendimiento del cultivo de maíz. La experiencia se llevó a cabo en la Estación Experimental Agropecuaria Anguil, INTA. Se realizaron determinaciones de agua útil y nitrato en el perfil del suelo, eficiencia del uso del agua (EUA) y producción de biomasa aérea del CC, recuento de malezas y rendimiento de grano en el cultivo maíz (sucesor) para tres momentos de quemado de los CC. Los resultados mostraron una mayor producción de biomasa aérea del CC y una mayor EUA en agosto y septiembre que en julio. El contenido de agua y nitrato en el perfil del suelo disminuyó cuanto más se demoró el momento de quemado (MQ), afectando negativamente el rendimiento de maíz. No hubo diferencias en la cantidad malezas presentes en el cultivo, entre los estados v6 y v8, ni en el rendimiento de maíz por la aplicación o no de herbicidas. DOI: http://dx.doi.org/10.19137/semiarida.2016(01).11-18

Hydrogen‐doped In2O3 (In2O3:H) is highly conductive while maintaining extraordinary transparency, thus making it a very attractive material for applications in optoelectronic devices such as (multijunction) solar cells or light‐emitting devices. However, the corresponding metal/In2O3:H contacts may exhibit undesirably high resistances, significantly deteriorating device performance. To gain insight into the underlying efficiency‐limiting mechanism, hard X‐ray photoelectron spectroscopy is employed to in‐situ monitor annealing‐induced changes in the chemical structure of the Ag/In2O3:H interface system that is further complemented by ex‐situ electron microscopy analyses and contact resistance measurements. The observed evolution of the Ag‐ and In‐related photoelectron line intensities can be explained by significant intermixing across the Ag/In2O3:H interface. The corresponding lineshape broadening of the Ag 3d spectra is attributed to the formation of Ag2O and AgO, which becomes significant at temperatures above approximately 160 °C. However, after annealing to 300 °C, instead of the formation of an insulating AgOx interfacial layer, it is found i) In to be rather homogeneously distributed in the complete Ag/In2O3:H stack, ii) Ag diffusing into the In2O3:H, and iii) an improvement of the contact resistance rather than its often‐reported deterioration. [ABSTRACT FROM AUTHOR]