An optoelectronic framework enabled by low-dimensional phase-change films.

Accepted author version. The definitive version was published in: Nature 511, 206–211 (10 July 2014) doi:10.1038/nature13487The development of materials whose refractive index can be optically transformed as desired, such as chalcogenide-based phase-change materials, has revolutionized the media and data storage industries by providing inexpensive, high-speed, portable and reliable platforms able to store vast quantities of data. Phase-change materials switch between two solid states--amorphous and crystalline--in response to a stimulus, such as heat, with an associated change in the physical properties of the material, including optical absorption, electrical conductance and Young's modulus. The initial applications of these materials (particularly the germanium antimony tellurium alloy Ge2Sb2Te5) exploited the reversible change in their optical properties in rewritable optical data storage technologies. More recently, the change in their electrical conductivity has also been extensively studied in the development of non-volatile phase-change memories. Here we show that by combining the optical and electronic property modulation of such materials, display and data visualization applications that go beyond data storage can be created. Using extremely thin phase-change materials and transparent conductors, we demonstrate electrically induced stable colour changes in both reflective and semi-transparent modes. Further, we show how a pixelated approach can be used in displays on both rigid and flexible films. This optoelectronic framework using low-dimensional phase-change materials has many likely applications, such as ultrafast, entirely solid-state displays with nanometre-scale pixels, semi-transparent 'smart' glasses, 'smart' contact lenses and artificial retina devices.Engineering and Physical Sciences Research Council (EPSRC)OUP John Fell Fun

IL-22 Is Produced by Innate Lymphoid Cells and Limits Inflammation in Allergic Airway Disease

Interleukin (IL)-22 is an effector cytokine, which acts primarily on epithelial cells in the skin, gut, liver and lung. Both pro- and anti-inflammatory properties have been reported for IL-22 depending on the tissue and disease model. In a murine model of allergic airway inflammation, we found that IL-22 is predominantly produced by innate lymphoid cells in the inflamed lungs, rather than TH cells. To determine the impact of IL-22 on airway inflammation, we used allergen-sensitized IL-22-deficient mice and found that they suffer from significantly higher airway hyperreactivity upon airway challenge. IL-22-deficiency led to increased eosinophil infiltration lymphocyte invasion and production of CCL17 (TARC), IL-5 and IL-13 in the lung. Mice treated with IL-22 before antigen challenge displayed reduced expression of CCL17 and IL-13 and significant amelioration of airway constriction and inflammation. We conclude that innate IL-22 limits airway inflammation, tissue damage and clinical decline in allergic lung disease

Orientation dependent molecular electrostatics drives efficient charge generation in homojunction organic solar cells

Organic solar cells usually utilise a heterojunction between electron-donating (D) and electron-accepting (A) materials to split excitons into charges. However, the use of D-A blends intrinsically limits the photovoltage and introduces morphological instability. Here, we demonstrate that polycrystalline films of chemically identical molecules offer a promising alternative and show that photoexcitation of α-sexithiophene (α-6T) films results in efficient charge generation. This leads to α-6T based homojunction organic solar cells with an external quantum efficiency reaching up to 44% and an open-circuit voltage of 1.61 V. Morphological, photoemission, and modelling studies show that boundaries between α-6T crystalline domains with different orientations generate an electrostatic landscape with an interfacial energy offset of 0.4 eV, which promotes the formation of hybridised exciton/charge-transfer states at the interface, dissociating efficiently into free charges. Our findings open new avenues for organic solar cell design where material energetics are tuned through molecular electrostatic engineering and mesoscale structural control

Visualization and suppression of interfacial recombination for high-efficiency large-area pin perovskite solar cells

The performance of perovskite solar cells is predominantly limited by non-radiative recombination, either through trap-assisted recombination in the absorber layer or via minority carrier recombination at the perovskite/transport layer interfaces. Here, we use transient and absolute photoluminescence imaging to visualize all non-radiative recombination pathways in planar pin-type perovskite solar cells with undoped organic charge transport layers. We find significant quasi-Fermi-level splitting losses (135 meV) in the perovskite bulk, whereas interfacial recombination results in an additional free energy loss of 80 meV at each individual interface, which limits the open-circuit voltage (V) of the complete cell to ~1.12 V. Inserting ultrathin interlayers between the perovskite and transport layers leads to a substantial reduction of these interfacial losses at both the p and n contacts. Using this knowledge and approach, we demonstrate reproducible dopant-free 1 cm perovskite solar cells surpassing 20% efficiency (19.83% certified) with stabilized power output, a high V (1.17 V) and record fill factor (>81%)

Rapid cloning of disease-resistance genes in plants using mutagenesis and sequence capture

Wild relatives of domesticated crop species harbor multiple, diverse, disease resistance (R) genes that could be used to engineer sustainable disease control. However, breeding R genes into crop lines often requires long breeding timelines of 5–15 years to break linkage between R genes and deleterious alleles (linkage drag). Further, when R genes are bred one at a time into crop lines, the protection that they confer is often overcome within a few seasons by pathogen evolution1. If several cloned R genes were available, it would be possible to pyramid R genes2 in a crop, which might provide more durable resistance1. We describe a three-step method (MutRenSeq)-that combines chemical mutagenesis with exome capture and sequencing for rapid R gene cloning. We applied MutRenSeq to clone stem rust resistance genes Sr22 and Sr45 from hexaploid bread wheat. MutRenSeq can be applied to other commercially relevant crops and their relatives, including, for example, pea, bean, barley, oat, rye, rice and maize

Filterless narrowband visible photodetectors

Wavelength selective light detection is crucial for many applications such as imaging and machine vision. Narrowband spectral responses are required for colour discrimination and current systems use broadband photodiodes combined with optical filters. This approach increases architectural complexity, and limits of the quality of colour sensing. Here we report filterless, narrowband red, green, and blue photodiodes with tuneable spectral responses. The devices have simple planar junction architectures with the photoactive layer being a solution processed mixture of either an organohalide perovskite or lead halide semiconductor, and a neutral or cationic organic molecule. The organic molecules modify the optical and electrical properties of the photodiode and facilitate narrowing charge collection narrowing of the device's external quantum efficiency. These red, green, and blue photodiodes all possess full-width-at-half-maxima of <100 nm and performance metrics suitable for many imaging applications