Synergetic interfacial conductivity modulation dictating hysteresis evolution in perovskite solar cells under operation.

In this work, the configuration of compact TiO coating (c-TiO) interface as electron transport layer (ETL) in giving rise to loss and gain of fill factor (FF) and therefore modulation of hysteresis behavior in perovskite solar cells (PSCs) is investigated. For this purpose, PSCs based on planar compact TiO (c-TiO) as well as a scaffold-based architecture are studied. In the latter case c-TiO coats a hydrothermally grown titania nanorod scaffold.

Correlation between hysteresis dynamics and inductance in hybrid perovskite solar cells: studying the dependency on ETL/perovskite interfaces.

In this study, to elucidate the origin of inductance and its relationship with the phenomenon of hysteresis in hybrid perovskite solar cells (PSCs), two electron transport layer (ETL) structures have been utilized: (a) rutile titania nanorods grown over anatase titania (AR) and (b) anatase titania covering the rutile titania nanorods (RA). The rutile and anatase phases are prepared hydrothermal synthesis and spray pyrolysis, respectively. PSCs based on an ETL with an RA structure attain higher short-circuit current density () and open-circuit voltage () while showing a slightly lower fill factor (FF) compared with their AR counterparts.

Nanoengineering of NiO/MnO/GO Ternary Composite for Use in High-Energy Storage Asymmetric Supercapacitor and Oxygen Evolution Reaction (OER).

Designing multifunctional nanomaterials for high performing electrochemical energy conversion and storage devices has been very challenging. A number of strategies have been reported to introduce multifunctionality in electrode/catalyst materials including alloying, doping, nanostructuring, compositing, etc. Here, we report the fabrication of a reduced graphene oxide (rGO)-based ternary composite NiO/MnO/rGO (NMGO) having a range of active sites for enhanced electrochemical activity.

Nanoscale assembling of graphene oxide with electrophoretic deposition leads to superior percolation network in Li-ion electrodes: TiNbO/rGO composite anodes.

In this paper, electrophoretic deposition (EPD) is shown to promote nanoscale assembling of graphene oxide (GO) enabling the fabrication of highly homogeneous, robust, and capacity fade resistant composite titanium niobate (TiNb2O7, TNO)/rGO anodes upon reductive annealing. Control tests revealed that EPD is superior to conventional PVDF-based casting in maximizing the performance benefits from using reduced GO in Li-ion electrode fabrication as is the case of TNO that is plagued with conductivity and capacity fading problems. In this particular study, we show that there is a synergy developed between GO and EPD with the former (1) stabilizing the EPD suspension, (2) acting as a flexible binder net that affords mechanical integrity during the volume expansion of TNO, (3) serving as a conductive filler, and (4) contributing to Li-ion storage via pseudocapacitance.

Core hole screened electron energy loss calculations of beam damaged lithium fluoride.

A method of calculating the magnitude of the core hole screening of lithium materials is implemented for the simulation of Energy Loss Near Edge Structure (ELNES). ELNES is calculated for a range of lithium materials resulting in improved agreement between calculation and experiment. The technique uses linear response theory to relate the electron density to the core hole shielding contribution from the valence electrons in a crystal.

Progress and Status of Hydrometallurgical and Direct Recycling of Li-Ion Batteries and Beyond.

An exponential market growth of Li-ion batteries (LIBs) has been observed in the past 20 years; approximately 670,000 tons of LIBs have been sold in 2017 alone. This trend will continue owing to the growing interest of consumers for electric vehicles, recent engagement of car manufacturers to produce them, recent developments in energy storage facilities, and commitment of governments for the electrification of transportation. Although some limited recycling processes were developed earlier after the commercialization of LIBs, these are inadequate in the context of sustainable development.

Aqueous-based Binary Sulfide Nanoparticle Inks for CuZnSnS Thin Films Stabilized with Tin(IV) Chalcogenide Complexes.

CuZnSnS(CZTS) is a promising semiconductor material for photovoltaic applications,with excellent optical and electronic properties while boasting a nontoxic, inexpensive, andabundant elemental composition. Previous high-quality CZTS thin films often required eithervacuum-based deposition processes or the use of organic ligands/solvents for ink formulation,which are associated with various issues regarding performance or economic feasibility. To addressthese issues, an alternative method for depositing CZTS thin films using an aqueous-basednanoparticle suspension is demonstrated in this work.

Lithium Photo-intercalation of CdS-Sensitized WO Anode for Energy Storage and Photoelectrochromic Applications.

Integration of solar-energy harvesting and storage functions has attracted significant research attention, as it holds promise for ultimate development of light-chargeable devices. In this context, a functional nanocomposite anode that not only permits electrochemical energy storage through Li-ion photo-intercalation, but also exhibits potential for photoelectrochromic applications, was investigated. The nanocomposite is made of the Li-ion intercalation compound WO , thinly coated with TiO and sensitized by the photoactive semiconductor CdS.

Nanostructural and photo-electrochemical properties of solution spin-coated CuZnSnS-TiO nanorod forest films with an improved photovoltaic performance.

CuZnSnS (CZTS), other than in standard p-n junction device architecture, can be employed as a broad light absorber upon coating onto a wide bandgap electron conducting TiO film. Earlier CZTS sensitized TiO films have yielded low photoconversion efficiency and V. In this work, a water-ethanol solution spin coating approach has been applied to directly deposit CZTS nanocrystallites on rutile TiO nanorods grown on an FTO substrate (TNR) for evaluation in a sensitized solar cell configuration.

Understanding the phase formation kinetics of nano-crystalline kesterite deposited on mesoscopic scaffolds via in situ multi-wavelength Raman-monitored annealing.

Kesterite, a highly promising photo-absorbing crystalline form of CuZnSnS (CZTS), has been prepared via various routes. However, the lack of in-depth understanding of the dynamic phase formation process of kesterite leads to difficulties in optimizing its annealing conditions, hence its light harvesting performance. In this paper, in situ Raman monitored-annealing is applied to study the phase formation kinetics of nano-crystalline kesterite from a precursor deposited on a TiO mesoscopic scaffold.

Accelerated Removal of Fe-Antisite Defects while Nanosizing Hydrothermal LiFePO4 with Ca(2).

Based on neutron powder diffraction (NPD) and high angle annular dark field scanning transmission electron microscopy (HAADF-STEM), we show that calcium ions help eliminate the Fe-antisite defects by controlling the nucleation and evolution of the LiFePO4 particles during their hydrothermal synthesis. This Ca-regulated formation of LiFePO4 particles has an overwhelming impact on the removal of their iron antisite defects during the subsequent carbon-coating step since (i) almost all the Fe-antisite defects aggregate at the surface of the LiFePO4 crystal when the crystals are small enough and (ii) the concomitant increase of the surface area, which further exposes the Fe-antisite defects. Our results not only justify a low-cost, efficient and reliable hydrothermal synthesis method for LiFePO4 but also provide a promising alternative viewpoint on the mechanism controlling the nanosizing of LiFePO4, which leads to improved electrochemical performances.

Stability of arsenate-bearing Fe(III)/Al(III) co-precipitates in the presence of sulfide as reducing agent under anoxic conditions.

Currently, the co-precipitation of arsenate with ferric iron at molar ratios Fe(III)/As(V) ≥ 3 by lime neutralization produces tailings solids that are stable under oxic conditions. However not much is known about the stability of these hazardous co-precipitates under anoxic conditions. These can develop in tailings storage sites by the action of co-discharged reactive sulfides, organic reagent residuals or bacterial activity.

Spontaneous reaction between an uncharged lithium iron silicate cathode and a LiPF6-based electrolyte.

The reaction between an uncharged Li2FeSiO4 (LFS) cathode and a LiPF6-EC/DMC electrolyte is revealed by in situ XANES in coin cells. This study shows clear evidence of delithiation and iron oxidation in LFS prior to cycling. Subsequent cycling appears to partially restore the original lithiation level, an observation that needs to be taken into consideration in future LFS development work.

Growth of Cu2ZnSnS4 Nanocrystallites on TiO2 Nanorod Arrays as Novel Extremely Thin Absorber Solar Cell Structure via the Successive-Ion-Layer-Adsorption-Reaction Method.

Cu2ZnSnS4 (CZTS) is an environmentally benign semiconductor with excellent optoelectronic properties that attracts a lot of interest in thin film photovoltaics. In departure from that conventional configuration, we fabricate and test a novel absorber-conductor structure featuring in situ successive-ion-layer-adsorption-reaction (SILAR)-deposited CZTS nanocrystallites as a light absorber on one-dimensional TiO2 (rutile) nanorods as an electron conductor. The effectiveness of the nanoscale heterostructure in visible light harvesting and photoelectron generation is demonstrated with an initial short circuit current density of 3.

Incorporation of arsenic into gypsum: Relevant to arsenic removal and immobilization process in hydrometallurgical industry.

Gypsum precipitates as a major secondary mineral during the iron-arsenate coprecipitation process for the removal of arsenic from hydrometallurgical effluents. However, its role in the fixation of arsenic is still unknown. This work investigated the incorporation of arsenic into gypsum quantitatively during the crystallization process at various pHs and the initial arsenic concentrations.

Stability of continuously produced Fe(II)/Fe(III)/As(V) co-precipitates under periodic exposure to reducing agents.

Arsenic mobilized during ore processing necessitates its effective removal from process effluents and disposal in environmentally stable tailings. The most common method to accomplish this involves co-precipitation with excess ferric iron during lime neutralization. The precipitates produced are stable under oxic conditions.

Rate-dependent phase transitions in Li2FeSiO4 cathode nanocrystals.

Nanostructured lithium metal orthosilicate materials hold a lot of promise as next generation cathodes but their full potential realization is hampered by complex crystal and electrochemical behavior. In this work Li2FeSiO4 crystals are synthesized using organic-assisted precipitation method. By varying the annealing temperature different structures are obtained, namely the monoclinic phase at 400°C, the orthorhombic phase at 900°C, and a mixed phase at 700°C.

New insight into the atomic-scale bulk and surface structure evolution of Li4Ti5O12 anode.

Identifying the structure of electrodes at atomic-scale remains a key challenge but is a fertile realm for groundbreaking fundamental research in the advanced Li-ion battery material field. In this context, the subtle structure evolution taking place during lithiation/delithiation in the bulk/surface of Li(4)Ti(5)O(12) spinel (LTO) was probed using scanning transmission electron microscopy and found to undergo significant structure torque, namely Ti-O bond stretching/shrinking at different state-of-charge (SOC), which is not identified previously. This kind of nanostructure change plays an important role in facilitating the formation of capturing centers for the electron/hole pairs in a 3.

Direct imaging of layered O3- and P2-NaxFe1/2Mn1/2O2 structures at the atomic scale.

Using aberration-corrected scanning transmission electron microscopy (STEM) with high-angle annular-dark-field (HAADF) and annular-bright-field (ABF) techniques, the atomic-scale structures of the O3 and P2 phases of NaxFe1/2Mn1/2O2 are investigated systematically. The Na, transition metal M (Fe and Mn) and O columns are well revealed and precisely assigned to the O3 and P2 phase layered structures. The O3 phase sample demonstrates larger atomic site fluctuations along [001] direction but with less structural imperfections (e.

Green-engineered all-substrate mesoporous TiO(2) photoanodes with superior light-harvesting structure and performance.

Electrophoretic deposition (EPD) is employed successfully in a suspension of multicomponent TiO2 nanoparticulates of different sizes and morphologies to engineer a very robust bifunctional electrode structure for dye-sensitized solar cell (DSSC) applications that shows excellent light-harvesting and photoelectrochemical performance. Aqueous-synthesized anatase nanocrystallites and sub-micrometer-sized "sea urchin"-like rutile aggregates are formulated in a stable isopropanol suspension without resorting to binders or charging agents. Interestingly, extremely robust films are obtained because of the high surface reactivity, electrophoretic mobility, and unique morphology of the rutile aggregates.

Size-dependent maximization of upconversion efficiency of citrate-stabilized β-phase NaYF4:Yb(3+),Er(3+) crystals via annealing.

Upconversion materials show great potential in converting infrared light to visible for many optoelectronic and photovoltaic devices. One of the most promising upconverting materials is Yb(3+),Er(3+)- doped β-NaYF4. In this study, annealing is shown to have a significant impact on the phase, morphology, and upconversion luminescence of β-NaYF4:Yb(3+),Er(3+) crystals of varying sizes (300 nm, 700 nm, and 2.

A novel two-step coprecipitation process using Fe(III) and Al(III) for the removal and immobilization of arsenate from acidic aqueous solution.

Lime neutralization and coprecipitation of arsenate with iron is widely practiced for the removal and immobilization of arsenic from mineral processing effluents. However, the stability of the generated iron-arsenate coprecipitate is still of concern. In this work, we developed a two-step coprecipitation process involving the use of iron and aluminum and tested the stability of the resultant coprecipitates.

Enhanced performance of dye-sensitized solar cells by utilization of an external, bifunctional layer consisting of uniform β-NaYF₄:Er³⁺/Yb³⁺ nanoplatelets.

Uniform β-NaYF(4):Er(3+)/Yb(3+) hexagonal nanoplatelets were synthesized via a modified hydrothermal route, and the nanoplatelets were applied as an external, bifunctional layer in a novel DSC configuration consisting of only one internal TiO(2) transparent layer. Approximately 10% enhancements of photocurrent and overall DSC efficiency are demonstrated by the addition of the external layer, which exhibits two functions of light reflecting and near-infrared (NIR) light harvesting. The novel DSC configuration not only simplifies the DSC fabrication process but also eliminates charge recombination induced by the conducting up-converting nanocrystals when used internally thus opening the path for other more efficient up-converting nanocrystals to be designed and applied.

Near-infrared sunlight harvesting in dye-sensitized solar cells via the insertion of an upconverter-TiO₂ nanocomposite layer.

Er(3+),Yb(3+) co-doped LaF₃-TiO₂ nanocomposites (UC-TiO₂) are inserted as a middle layer in a novel tri-layer photoanode design (see Figure) of a dye-sensitized solar cell (DSSC). The Er(3+),Yb(3+) co-doped LaF₃ part of the nanocomposite helps capture near-infrared (NIR) light by converting it into visible light absorbable by the dye hence opening the road for the development of DSSCs with higher conversion efficiency and photocurrent output.