Interface Modification for Energy Levels Alignment and Charge Extraction in CsPbI3_3 Perovskite Solar Cells

In perovskite solar cells (PSCs) energy levels alignment and charge extraction at the interfaces are the essential factors directly affecting the device performance. In this work, we present a modified interface between all-inorganic CsPbI$_3$ perovskite and its hole selective contact (Spiro-OMeTAD), realized by a dipole molecule trioctylphosphine oxide (TOPO), to align the energy levels. On a passivated perovskite film, by n-Octyl ammonium Iodide (OAI), we created an upward surface band-bending at the interface by TOPO treatment. This improved interface by the dipole molecule induces a better energy level alignment and enhances the charge extraction of holes from the perovskite layer to the hole transport material. Consequently, a Voc of 1.2 V and high-power conversion efficiency (PCE) of over 19% were achieved for inorganic CsPbI$_3$ perovskite solar cells. Further, to demonstrate the effect of the TOPO dipole molecule, we present a layer-by-layer charge extraction study by transient surface photovoltage technique (trSPV) accomplished by charge transport simulation.Comment: 20 pages, 4 Figure

Triple A-Site Cation Mixing in 2D Perovskite-Inspired Antimony Halide Absorbers for Efficient Indoor Photovoltaics

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Comparison of seven prognostic tools to identify low-risk pulmonary embolism in patients aged <50 years

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Common variants in Alzheimer's disease and risk stratification by polygenic risk scores.

Funder: Funder: Fundación bancaria ‘La Caixa’ Number: LCF/PR/PR16/51110003 Funder: Grifols SA Number: LCF/PR/PR16/51110003 Funder: European Union/EFPIA Innovative Medicines Initiative Joint Number: 115975 Funder: JPco-fuND FP-829-029 Number: 733051061Genetic discoveries of Alzheimer's disease are the drivers of our understanding, and together with polygenetic risk stratification can contribute towards planning of feasible and efficient preventive and curative clinical trials. We first perform a large genetic association study by merging all available case-control datasets and by-proxy study results (discovery n = 409,435 and validation size n = 58,190). Here, we add six variants associated with Alzheimer's disease risk (near APP, CHRNE, PRKD3/NDUFAF7, PLCG2 and two exonic variants in the SHARPIN gene). Assessment of the polygenic risk score and stratifying by APOE reveal a 4 to 5.5 years difference in median age at onset of Alzheimer's disease patients in APOE ɛ4 carriers. Because of this study, the underlying mechanisms of APP can be studied to refine the amyloid cascade and the polygenic risk score provides a tool to select individuals at high risk of Alzheimer's disease

First-Principles Design of New Electrodes for Proton-Conducting Solid-Oxide Electrochemical Cells: A-Site Doped Sr2Fe1.5Mo0.5O6-δ Perovskite

Electrolyzer and fuel cells based on proton-conducting solid oxide ceramics (PC-SOEC/FC) are gaining wide interest as promising green technologies for H-2 production and conversion. Despite major advances in PC electrolytes, large-scale deployment of PC-SOEC/FC has been hindered by severe limitations at electrodes, which must ensure catalytic activity, electronic conduction, and high proton diffusion rates. Designing electrodes with mixed proton and electron conduction capability represents a great challenge. Several attempts have been based on composite materials made of common electrocatalysts and PC electrolytes, but the resulting electrodes have often suffered stability and conductivity problems. Inspired by the good performance in PC regime of some perovskite oxides, here we propose an alternative approach by designing a new single-phase triple-conducting oxide (TCO) from the recently proposed and well-tested mixed ion-electron conductive electrocatalyst Sr2Fe1.5Mo0.5O6-delta (SFMO) double perovskite. We investigated with first-principles methods (DFT+U) the key processes that promote proton transport, i.e., oxygen vacancy formation, water dissociative incorporation into the defective lattice, and proton transfer along the oxide sublattice. We focused on SFMO and A-substituted derivatives with Ba or K cations. Both dopants lower the proton migration barrier of SFMO, thus improving proton transport effectiveness. In particular, we found K-doped SFMO to be the best candidate thanks to its peculiar and very favorable structural and electronic properties. Moreover, from our ab initio analysis, we identified a general design principle to enhance proton transport in perovskite oxides at the nanoscale. Our computational results can be easily implemented to develop and test new low-cost TCO-based electrodes for PC-SOEC/FC

K-doped Sr2Fe1.5Mo0.5O6-d predicted as a bifunctional catalyst for air electrodes in proton-conducting solid oxide electrochemical cells

Perovskite oxides are promising electrodes for oxygen evolution and reduction reactions (OER/ORR), but it is difficult for a single material to catalyze both reactions efficiently. We investigated using first-principles calculations the K-doped Sr2Fe1.5Mo0.5O6-d mixed proton-electron conducting oxide. We found that aliovalent doping tunes the electronic features to be optimal for the ORR and lattice expansion-driven surface reconstruction stabilizes the key ∗OOH intermediate for the OER. The resulting ORR/OER overpotentials are very low (∼0.5 V), suggesting the application of this material as an air electrode in reversible solid oxide electrochemical cells

From oxide to proton conduction: A quantum-chemical perspective on the versatility of Sr2Fe1.5Mo0.5O6−δ-based materials

Sr2Fe1.5Mo0.5O6-delta (SFMO) is a promising electrode material for solid oxide electrochemical cells. This perspective highlights the role of first-principles investigations in unveiling SFMO structural, electronic, and defect properties. In particular, DFT+U provides a reliable and convenient tool for extensive studies on strongly correlated transition-metal oxides, as SFMO and related systems. The SFMO excellent performances are ascribed to a mixed oxide ion-electron conductor character. Crucial features are the easy formation of oxygen vacancies and the low oxide migration barrier heights. Aliovalent doping with K+ enables convenient hydration and effective proton transport in bulk SFMO. This opens a route toward new promising triple-conductor oxides. Besides discussion of specific SFMO applications, our results help to uncover general perovskite-oxide features and new design principles for oxide- and proton-conducting solid oxide fuel cell electrodes

Structure and energy level alignment at the dye-electrode interface in p-type DSSCs: new hints on the role of anchoring modes from ab initio calculations

p-type dye-sensitized solar cells (DSSCs) represent the complementary photocathodes to the well-studied n-type DSSCs (Grätzel cells), but their low performances have hindered the development of convenient tandem solar cells based on cost-effective n- and p-type DSSCs. Because of their low efficiencies, experimental investigations highlighted the role of hole-electron transport processes at the dye-electrode interface. However, the effects of the dye anchoring groups on interfacial electronic features are still unclear. We report here a first principles study of a benchmark p-type DSSC model, namely the widely used Coumarin-based dye C343 adsorbed on the p-NiO surface. Together with the original carboxylic acid, we test the alternative phosphonic acid as the anchoring group. We investigate binding energies, structural features and electronic energy level alignments: our results highlight that these properties are highly sensitive to the binding modes. In particular, both the chemical nature of the anchoring group and the binding mode strongly affect the thermodynamic driving force for the dye-electrode hole injection process. From analysis of the electronic densities, we find that favorable driving forces are correlated with small values of the interfacial electrostatic dipole that is formed upon dye adsorption. From our results, we derive new hints for improving open circuit potential and the hole injection process in p-type DSSCs based on NiO electrodes

Non-innocent dissociation of H2O on GaP(110): Implications for electrochemical reduction of CO2

The structural and electronic properties of the GaP(110)/H 2O interface have been investigated by first-principles density functional theory calculations. Our results suggest that hydride-like H atoms are present on the surface as a consequence of the dissociation of water in contact with the GaP surface. This feature opens up a new feasible reduction pathway for CO 2 where the GaP(110) surface is the electrochemically active entity

Ab initio study of PbCr(1- x)SxO4 solid solution: An inside look at Van Gogh Yellow degradation

Van Gogh Yellow refers to a family of lead chromate pigments widely used in the 19th century and often mixed with lead sulfate to obtain different yellow hues. Unfortunately, some paintings, such as the famous Sunflowers series, suffered degradation problems due to photoactivated darkening of once bright yellow areas, especially when irradiated with UV light. Recent advanced spectroscopic analyses have proved that this process occurs mostly where the pigment presents a sulfur-rich orthorhombic phase of a PbCr(1-x)SxO4 solid solution, while chromium-rich monoclinic phases are lightfast. However, the question of whether degradation is purely a surface phenomenon or if the bulk properties of sulfur rich pigments trigger the process is still open. Here, we use first-principles calculations to unveil the role of sulfur in determining important bulk features such as structure, stability, and optical properties. From our findings, we suggest that degradation occurs via an initial local segregation of lead sulfate that absorbs at UV light wavelengths and provides the necessary energy for subsequent reduction of chromate ions into the greenish chromic oxide detected in experiments. In perspective, our results set reliable scientific foundations for further studies on surface browning phenomena and can help to chose the best strategy for the proper conservation of art masterpieces