Molybdenum oxide is used as a low-resistance anode interfacial layer in applications such as organic light emitting diodes and organic photovoltaics. However, little is known about the correlation between its stoichiometry and electronic properties, such as work function and occupied gap states. In addition, despite the fact that the knowledge of the exact oxide stoichiometry is of paramount importance, few studies have appeared in the literature discussing how this stoichiometry can be controlled to permit the desirable modification of the oxide's electronic structure. This work aims to investigate the beneficial role of hydrogenation (the incorporation of hydrogen within the oxide lattice) versus oxygen vacancy formation in tuning the electronic structure of molybdenum oxides while maintaining their high work function. A large improvement in the operational characteristics of both polymer light emitting devices and bulk heterojunction solar cells incorporating hydrogenated Mo oxides as hole injection/extraction layers was achieved as a result of favorable energy level alignment at the metal oxide/organic interface and enhanced charge transport through the formation of a large density of gap states near the Fermi level.

The surface, interfaces and grain boundaries of a halide perovskite film carry critical tasks in achieving as well as maintaining high solar cell performance due to the inherently defective nature...

Synopsis ER aminopeptidase 1 (ERAP1), ER aminopeptidase 2 (ERAP2) and Insulin Regulated aminopeptidase (IRAP) are three homologous enzymes that play critical roles in the generation of antigenic peptides. These aminopeptidases excise amino acids from N-terminally extended precursors of antigenic peptides in order to generate the correct length epitopes for binding onto MHC class I molecules. The specificity of these peptidases can affect antigenic peptide selection, but has not yet been investigated in detail. In the present study we utilized a collection of 82 fluorogenic substrates to define a detailed selectivity profile for each of the three enzymes and to probe structural and functional features of the primary specificity (S1) pocket. Molecular modeling of the three S1 pockets reveals substrate-enzyme interactions that are critical determinants for specificity. The substrate selectivity profiles suggest that IRAP largely combines the S1 specificity of ERAP1 and ERAP2, consistent with its proposed biological function. IRAP however, does not achieve this dual specificity by simply combining structural features of ERAP1 and 2, but rather by a unique amino acid change at position 541. Our results provide insights on antigenic peptide selection and may prove valuable in designing selective inhibitors or activity markers for this class of enzymes.

Near-infrared light-emitting diodes based on solution-processed semiconductors, such as organics, halide perovskites and colloidal quantum dots, have emerged as a viable technological platform for biomedical applications, night vision, surveillance and optical communications. The recently gained increased understanding of the materials structure-photophysical property relationship has enabled the design of efficient emitters leading to devices with external quantum efficiencies exceeding 20%. Despite significant strides made, challenges remain in achieving high radiance, reducing efficiency roll-off, and extending operating lifetime. This review summarizes recent advances on emissive materials synthetic methods and device key attributes that collectively contribute to improved performance of the fabricated light-emitting devices.Light-emitting diodes (LEDs) with emission in the near-infrared (NIR) part of the spectrum (700-2500 nm) (termed as NIR-LEDs) support a large variety of applications such as optical diagnosis and biomedical imaging 1 , optical communication, remote sensing, security, night vision and data storage 2 .The specific application field determines the spectral range of interest within the NIR (Fig. 1a). With regard to in vivo bioimaging, the semi-transparency of biological tissues, oxygenated and deoxygenated blood in specific NIR wavelength regions, also known as biological windows, makes NIR particularly appealing for optical imaging, biomedical sensing and photodynamic therapy. In the field of optical wireless communications, the spectral range is also divided in bands, which correlate with the wavelength regions where optical fibres have small transmission losses 3 . NIR-LEDs are also in demand 3 for security authentication, optogenetics, life-cycle management of crops, light fidelity and surveillance 4 .Common NIR-LEDs are epitaxial heterostructures of III-V inorganic semiconductors (e.g. GaAs, InGaAs, InGaAlAs) [5][6][7] . Commercially available products also employ inorganic phosphors, namely compounds doped with transition metals 8 , or rare-earth trivalent ions 9 . An external quantum efficiency (EQE) of 72% at 880 nm has been reported for an AlGaAs/GaAs/AlGaAs III-V-LED 6 , and 44.5% at 775 nm for LEDs based on LaMgGa 11 O 19 :Cr 3+ phosphors 10 . However, III-V LEDs require post fabrication substrate replacement with high reflective mirror structures to increase their poor power output originating from the refractive index mismatch between those materials (>3.0) 7 and common substrates.Additionally, inorganic phosphors require very high temperature sintering treatment (above 1000 o C).These processing requirements are an obstacle for low-cost, handheld portable implementations. Organic (OSCs) 11 , metal-halide perovskite (HPs) 12 , and colloidal quantum dot (QD) 13 semiconductors, can be processed using low cost and low temperature methods on a wide variety of substrates. For example via solution-based processes such as ink-jet printing, doctor blade and spray coating (Fig. 1b). These...

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We present a novel "brick and mortar" strategy for creating highly efficient transparent TiO 2 coatings for photocatalytic and photovoltaic applications. Our approach is based on the fusion of preformed titania nanocrystalline "bricks" through surfactant-templated sol-gel titania "mortar", which acts as a structuredirecting matrix and as a chemical glue. The similar chemical composition of both bricks and mortar leads to a striking synergy in the interaction of crystalline and amorphous components, such that crystallization is enhanced upon thermal treatment and highly porous and highly crystalline structures are formed at very mild conditions. Coatings with a broad variety of periodic mesostructures and thicknesses ranging from few nanometers to several micrometers are accessible using the same organic template, and the final structures are tunable by varying the fraction of the "bricks". The beneficial combination of crystallinity and porosity leads to greatly enhanced activity of the films in photocatalytic processes, such as the photooxidation of NO. Acting as the active layers in dye-sensitized solar cells, films of only 2.7 µm in thickness exhibit a conversion efficiency of 6.0%.

Over the last decade, there has been increasing interest in transferring the research advances in radiofrequency (RF) rectifiers, the quintessential element of the chip in the RF identification (RFID) tags, obtained on rigid substrates onto plastic (flexible) substrates. The growing demand for flexible RFID tags, wireless communications applications and wireless energy harvesting systems that can be produced at a low-cost is a key driver for this technology push. In this topical review, we summarise recent progress and status of flexible RF diodes and rectifying circuits, with specific focus on materials and device processing aspects. To this end, different families of materials (e.g. flexible silicon, metal oxides, organic and carbon nanomaterials), manufacturing processes (e.g. vacuum and solution processing) and device architectures (diodes and transistors) are compared. Although emphasis is placed on performance, functionality, mechanical flexibility and operating stability, the various bottlenecks associated with each technology are also addressed. Finally, we present our outlook on the commercialisation potential and on the positioning of each material class in the RF electronics landscape based on the findings summarised herein. It is beyond doubt that the field of flexible high and ultra-high frequency rectifiers and electronics as a whole will continue to be an active area of research over the coming years.

Here, we report on the dual functionality of tungsten oxide for application as an efficient electron and hole injection/transport layer in organic light‐emitting diodes (OLEDs). We demonstrate hybrid polymer light‐emitting diodes (Hy‐PLEDs), based on a polyfluorene copolymer, by inserting a very thin layer of a partially reduced tungsten oxide, WO2.5, at the polymer/Al cathode interface to serve as an electron injection and transport layer. Significantly improved current densities, luminances, and luminous efficiencies were achieved, primarily as a result of improved electron injection at the interface with Al and transport to the lowest unoccupied molecular orbital (LUMO) of the polymer, with a corresponding lowering of the device driving voltage. Using a combination of optical absorption, ultraviolet spectoscopy, X‐ray photoelectron spectroscopy, and photovoltaic open circuit voltage measurements, we demonstrate that partial reduction of the WO3 to WO2.5 results in the appearance of new gap states just below the conduction band edge in the previously forbidden gap. The new gap states are proposed to act as a reservoir of donor electrons for enhanced injection and transport to the polymer LUMO and decrease the effective cathode workfunction. Moreover, when a thin tungsten oxide film in its fully oxidized state (WO3) is inserted at the ITO anode/polymer interface, further improvement in device characteristics was achieved. Since both fully oxidized and partially reduced tungsten oxide layers can be deposited in the same chamber with well controlled morphology, this work paves the way for the facile fabrication of efficient and stable Hy‐OLEDs with excellent reproducibility.