Dr Daniel Commandeur

Three-dimensional all-inorganic perovskite solar cells have been built using vertically aligned conductive zinc oxide nanorods as the electron-transport layer and optical waveguide. Yttrium doping improved the conductivity and hence the electron transportation of the ZnO, achieving a 3-fold improvement of the solar cell efficiency. The vertically aligned nanorods acted as optical waveguides and a scaffold, which improved photoabsorption of the perovskite semiconductor by increasing the layer thickness. Our device structure was completed with an exfoliated multilayer graphite back contact for effective hole extraction. The ZnO was most significantly modified by nanometer scale coatings of TiO2 in order to passivate the surface and reduce charge recombination, as measured by photoluminescence spectroscopy. This led to greatly improved charge transfer. This strategy led to an overall nine times enhancement in the solar cell efficiency, yielding a competitive top value of 5.83%. More importantly, the all-inorganic solar cells demonstrated excellent stability, showing no decline in initial performance after 1000 h storage in ambient conditions. This work presents yttrium doped ZnO nanorods as a suitable replacement for mesoporous TiO2, achieving a high short circuit current of 10.5 mA cm(-2) for CsPbBr3 perovskite devices.

As perovskite solar cells have yielded impressive efficiency at a low cost, the focus has shifted to increase their service life as they are plagued by rapid degradation. Refreshingly, CsPbBr3 solar cells built on a conductive ZnO nanowire electron transport layer with a graphite counter electrode not only avoided degradation but also showed some of the reverse trends under specific conditions, showing significant maturation over time. In this work, this phenomenon is first confirmed to be reproducible from a large sample size with on average a 40 ± 10% increase in efficiency after 2 weeks of storage. To explore the mechanisms of this positive maturing effect, samples were stored under different controlled conditions and tested regularly by using scanning electron microscopy, powder X-ray diffraction, current–voltage (IV) curves, and impedance spectroscopy. The samples stored in a methanol atmosphere presented a dramatic positive effect, giving a 4-fold increase in efficiency after 2 days of storage. However, in the saturated H2O environment, the device performance rapidly degraded. By observing the solar cell performance affected by various storage conditions, including various solvent vapors, light illumination, and an inert gas (N2), we suggest three possible complementary factors. First, solvents shifted the equilibrium of crystal phase ratio of CsPbBr3 to CsPb2Br5. Second, the CsPbBr3 grain size was reduced with improved electrical contact with the conductive ZnO nanowires. Finally, ion migration and accumulation lead to the formation of local p–n junctions at crystal grain boundaries with improved charge separation. This was evidenced by the increased kinetic relaxation times on ionic time scales. Rather than degrading, under appropriate conditions, these cells were able to increase in value/efficiency over storage time. By elucidating the underlying mechanisms for the CsPbBr3 solar cell stability, the work offers guidelines for improving perovskite solar cell long-term efficiency.

Rational designs of the conductive layer below photocatalytic films determine the efficiency of a photoanode for solar water oxidation. Generally, transparent conductive oxides (TCOs) are widely used as a conductive layer. In this mini review, the fundamentals of TCOs are explained and typical examples of nanoscale TCOs are presented for application in photoelectrochemical (PEC) water oxidation. In addition, hybrid structures formed by coating other photocatalysts on nanoscale TCOs are discussed. In the future, the nanostructured electrode may inspire the design of a series of optoelectronic applications. Rational designs of the conductive layer below photocatalytic films determine the efficiency of a photoanode for solar water oxidation.

Liqui-Pellet is considered to be the next generation oral dosage form. It is highly commercially feasible unlike its predecessor, liquisolid formulation. Liqui-Pellet uses Liqui-Mass system, allowing the formulation to overcome some of the critical drawbacks in liquisolid technology, which persisted more than two decades. These drawbacks include poor flowability, poor compressibility and inability for high dose without product being too heavy and bulky for swallowing. The investigation is an extension of the previous work on the Liqui-Pellet. In order to make this novel oral delivery system a commercial product, it is prudent to further understand the parameters affecting its drug release rate. Two major parameters affecting the dissolution rate that is investigated are water and liquid vehicle (Tween 80) contents. It is found out that reducing water content (from 8.62 ml to 4.76 ml which is 1.9 ml/0.95 ml per 20 g of API and excipients) and increasing Tween 80 concentration (from 28% w/w to 32 or 36% w/w) in naproxen Liqui-Pellet results to an increase in drug release rate; however, there is a limit of how much water and Tween 80 can be employed. Outside of this range limit, the formulation would fail to produce Liqui-Pellet due to agglomeration. The range limit of granulation liquid and liquid vehicle content are dependent on one another. In the successful formulation where Liqui-Pellets are formed, the excellent-good flow properties, resistant to friability and narrow size distribution makes it ideal for commercial production. SEM of the Liqui-Pellet shows a smooth surface which is ideal for coating. The solid state analysis via XRPD and DSC indicated reduced crystallinity of the drug which is expected. (C) 2020 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.

A combinatorial library of twenty-three, phase pure, near-NMC111 (LiNi0.33Mn0.33Co0.33O2) compositions were synthesised and their electrochemical performance, was mapped (in lithium ion half-cells). Each of the 23 compositions was made in series, using a two-step process of 1) a rapid initial continuous hydrothermal precipitation, followed by 2) solid state lithiation. The 23 lithiated NMC samples were then subjected to analytical methods including electron microscopy (selected samples), Powder X-ray Diffraction and electrochemical tests in half cell Li-ion configurations versus Li metal. A sample with a Ni:Mn:Co (NMC) ratio of 39:28:33, revealed a specific capacity of 150 mA h g(-1) at a C/20 rate, which was 63 and 43% greater capacity than NMC111 and NMC433 samples produced in this work, respectively. The sample with NMC ratio 47:25:28, showed the best capacity retention characteristics, retaining 70% of its C/20 capacity at 1C, after 40 cycles. Further analysis of all the samples by cyclic voltammetry and electrochemical impedance spectroscopy, allowed compositional mapping of diffusion coefficients. Overall, the mapping data revealed a gradual change of properties across compositional space, which has validated our combinatorial approach and allowed identification of the optimum performing near-NMC111 cathode materials. (C) 2022 The Chinese Ceramic Society. Production and hosting by Elsevier B.V.

Herein, the direct synthesis of phase-pure lithium aluminum titanium phosphate (Li1.3Al0.3Ti1.7(PO4)(3), LATP) solid-electrolyte powder in 220 min and relatively low temperatures (850 degrees C) is achieved via a new (cyclic) fast heat treatment (c-FHT) route. The complex structural evolution highlights rate-limited lithium incorporation of intermediate metal phosphates formed prior to the final phase-pure LATP. The prepared LATP product powder displays similar bulk (2 x 10(-10 )cm(2) s(-1)) and local (3 x 10(-10 )cm(2) s(-1)) values for lithium diffusion coefficients (D-Li) characterized by electrochemical impedance spectroscopy and muon spin relaxation (mu SR), respectively. The similarity between both D-Li values suggests excellent retention of inter- and intraparticle lithium diffusion, which is attributed to the absence of deleterious surface impurities such as AlPO4. A low-energy barrier (E-a = 73 meV) of lithium diffusion is also estimated from the mu SR data.

For the first time, hematite ( -Fe2O3) crystals were electrochemically deposited over vertically aligned conductive zinc oxide nanorods (NR) to form a specially designed 3D heterostructure with a unique triple layer structure. The structure formed with a thin layer of ZnFe2O4 sandwiched between the hematite and the ZnO, which forms a barrier to reduce the back migration of holes. Hence, the charge separation is significantly improved. The small unequal bandgaps of -Fe2O3 and ZnFe2O4 help to enhance and broaden visible light absorption. The electron transportation was further improved by yttrium doping in the ZnO (YZnO) NRs, resulting in increased conductivity. This allowed the vertically aligned NRs to perform as electron highways, which also behave as effective optical waveguides for improved light trapping and absorption, since ZnO absorbs little visible light. All these benefits made the unique structures suitable for high performance photoelectrochemical (PEC) water splitting. Optimisation of -Fe2O3 thickness led to a photocurrent density improvement from 0.66 to 0.95 mA cm−2 at 1.23 VRHE. This was further improved to 1.59 mA cm−2 by annealing at 550 °C for 3 h, representing a record-breaking photocurrent for -Fe2O3/ZnO systems. Finally IPCE confirmed the successful generation and transfer of photoelectrons under visible light excitation in the specifically designed heterostructure photoanode, with 5% efficiency for blue light, and 15% for violet light.

Hybrid metal-oxide nanostructures have drawn much attention recently because of their ability to overcome the disadvantages of each individual material to achieve high-performance solar water splitting. Using anodic electrochemical deposition, hybrid polycrystalline goethite (alpha-FeOOH) and hematite (alpha-Fe2O3) nanosheets (GOE/HM NSs) were success fully synthesized on yttrium-doped ZnO nanorods (YZO NRs). The unique morphology, with GOE/HM NSs wrapped around the length of vertically aligned YZO NRs, is favorable for light harvesting, charge transfer, and charge transportation. The density and the effective surface area of NSs were optimized for achieving a fine balance between light absorption and charge transportation between the photoanode and the electrolyte. The samples showed much improved water splitting efficiency under both UV and visible-light excitation, which represents the synergistic effects of GEO/ HM NSs with YZO NRs. UV-vis absorption and incident photon-to-current conversion efficiency measurements demonstrated appropriate band alignment at interfaces, in addition to the reduced band gap energy. Electrochemical impedance spectroscopy measurements showed greatly reduced charge-transfer resistance. The hybrid material achieved an increase in the water splitting ability by a factor of 4.5 from pristine ZnO NRs (0.2 mA cm(-2)) to GOE/HM NSs-coated YZO NRs (0.92 mA cm(-2)). This represents a highly competitive strategy for improving the ability of ZnO for water splitting.