Search

Narrowband photodetectors (PDs) are sought after for many applications requiring selective spectral response. The most common systems combine optical bandpass filters with broadband photodiodes. This work reports a method to obtain a narrowband response in a perovskite PD by the monolithic integration of a perovskite photoconductor and a perovskite photodiode. The spectral response of the tandem PD is determined by the bandgap energy difference of the two perovskites, and exhibits a full width at half maximum below 85 nm, an external quantum efficiency up to 68% and a high specific detectivity of ≈1012 Jones in reverse bias, enabling the device to detect weak light signals. The absorption profile of the narrowband PD can be tuned by changing the thickness and bandgap of the wide bandgap perovskite absorber.

The oil and democracy nexus has been traditionally studied from an oil-impedes-democracy perspective, where researchers demonstrated that more oil leads to less democracy. The relationship has been rarely flipped and researchers have rarely inquired as to what extent less oil fosters democratization. This thesis flips the relationship between oil and democracy and asks: “how do negative oil price shocks affect democratization in oil dependent autocratic countries?” Based on rentier effect theory and on selectorate theory, it derives several hypotheses as to the general relationship and as to the mechanism that drives it. It hypothesizes that negative oil price shocks lead to democratization. In addition, it hypothesizes that the effect is conditional on an increase in taxation, a decrease in public goods provision, or a decrease in repression. Using a two way fixed effects model and a moderator model, this thesis finds no effect of negative oil price shocks on democratization, not even conditional ones except for a small effect conditional on a decrease in repression.

Lead halide perovskites (ABX3) are generally formed from a reaction of the lead halide salt (BX2) with the halide salt of the A cation (AX). The effects of varying film compositions as result of non-stoichiometric precursor ratios on electronic properties of halide perovskites are currently under debate. It is imperative, but experimentally challenging, to determine the chemical composition of thin films as a function of precursor ratio for a full understanding of the effect. Herein we report a precise quantification of the methylammonium (MA) content in differently fabricated films of MAPbI3 via infrared (IR) spectroscopy. We compare the thin film data to the first high quality dielectric function obtained from single crystals with IR ellipsometry. For spin-coated samples, we find that the MAI/PbI2 ratio in solution has an effect on the MA content in the resulting thin films which is in the range of 77-106% compared to single crystals. For co-evaporated samples, we show that a very similar range of MA co...

We report a series of seven cationic heteroleptic copper(I) complexes of the form [Cu(P^P)(dmphen)]BF4, where dmphen is 2,9-dimethyl-1,10-phenanthroline and P^P is a diphosphine chelate, in which the effect of the bite angle of the diphosphine ligand on the photophysical properties of the complexes was studied. Several of the complexes exhibit moderately high photoluminescence quantum yields in the solid state, with ΦPL of up to 35%, and in solution, with ΦPL of up to 98%. We were able to correlate the powder photoluminescence quantum yields with the % Vbur of the P^P ligand. The most emissive complexes were used to fabricate both organic light-emitting diodes and light-emitting electrochemical cells (LECs), both of which showed moderate performance. Compared to the benchmark copper(I)-based LECs, [Cu(dnbp)(DPEPhos)]+ (maximum external quantum efficiency, EQEmax = 16%), complex 3 (EQEmax = 1.85%) showed a much longer device lifetime (t1/2 = 1.25 h and >16.5 h for [Cu(dnbp)(DPEPhos)]+ and complex 3, respectively). The electrochemiluminescence (ECL) properties of several complexes were also studied, which, to the best of our knowledge, constitutes the first ECL study for heteroleptic copper(I) complexes. Notably, complexes exhibiting more reversible electrochemistry were associated with higher annihilation ECL as well as better performance in a LEC.

Funding: C.L. thanks the Prof. & Mrs Purdie Bequests Scholarship and AstraZeneca for a PhD Studentship. The St Andrews researchers thank the Engineering and Physical Sciences Research Council (EP/M02105X/1 and EP/R035164/1) for financial support. A.K.P. acknowledges the Leverhulme Trust and the University of St Andrews for an Early Career Fellowship (ECF-2017-326). H.J.B. and M.S. acknowledge funding from the Spanish Ministry of Science, Innovation and Universities (MAT2017‐88821‐R and RYC-2016-21316, respectively). C.F.H. acknowledges the support of the Australian Research Council (ARC) Discovery grant scheme (DP200102947). We report a series of seven cationic heteroleptic copper(I) complexes of the form [Cu(P^P)(dmphen)]BF4, where dmphen is 2,9-dimethyl-1,10-phenanthroline and P^P is a diphosphine chelate, in which the effect of the bite angle of the diphosphine ligand on the photophysical properties of the complexes was studied. Several of the complexes exhibit moderately high photoluminescence quantum yields in the solid state, with ΦPL of up to 35%, and in solution, with ΦPL of up to 98%. We were able to correlate the powder photoluminescence quantum yields with the % Vbur of the P^P ligand. The most emissive complexes were used to fabricate both organic light-emitting diodes and light-emitting electrochemical cells (LECs), both of which showed moderate performance. Compared to the benchmark copper(I)-based LECs, [Cu(dnbp)(DPEPhos)]+ (maximum external quantum efficiency, EQEmax = 16%), complex 3 (EQEmax = 1.85%) showed a much longer device lifetime (t1/2 = 1.25 h and >16.5 h for [Cu(dnbp)(DPEPhos)]+ and complex 3 , respectively). The electrochemiluminescence (ECL) properties of several complexes were also studied, which, to the best of our knowledge, constitutes the first ECL study for heteroleptic copper(I) complexes. Notably, complexes exhibiting more reversible electrochemistry were associated with higher annihilation ECL as well as better performance in a LEC. Postprint

We report a series of seven cationic heteroleptic copper(I) complexes of the form [Cu (P^P) (dmphen)]BF4, where dmphen is 2,9-dimethyl-1,10-phenanthroline and P^P is a diphosphine chelate, in which the effect of the bite angle of the diphosphine ligand on the photophysical properties of the complexes was studied. Several of the complexes exhibit moderately high photoluminescence quantum yields in the solid-state, with ΦPL of up to 35%, and in solution, with ΦPL of up to 98%. We were able to correlate the powder photoluminescence quantum yields with the %Vbur of the P^P ligand. The most emissive complexes were used to fabricate both organic light-emitting diodes (OLEDs) and light-emitting electrochemical calls (LECs), both of which showed moderate performance. Compared to the benchmark Cu(I)-based LECs, [Cu(dnbp)(DPEPhos)]+ (EQEmax = 16%), complex 3 (EQEmax = 1.85%) showed much longer device lifetime (t1/2 = 1.25 h and >16.5 h for [Cu(dnbp)(DPEPhos)]+ and complex 3, respectively). The electrochemiluminescent properties of several complexes were also studied which to the best of our knowledge constitutes the first ECL study for heteroleptic copper (I) complexes. Notably, complexes exhibiting more reversible electrochemistry were associated with higher annihilation ECL as well as better performance in an LEC device.

Background: Pneumonia is a leading cause of death worldwide and is a major healthcare challenge for HIV-infected persons. Despite this, the etiology of pneumonia in this population remains poorly understood. Methods: We employed a combination of bulk RNA sequencing of bronchoalveolar lavage fluid and standard culture- and PCR-based diagnostics to survey the landscape of transcriptionally active respiratory pathogens in 217 Ugandan patients with HIV who were hospitalized for pneumonia. Findings: A microbiologic diagnosis was obtained in 211 (97.2%) of individuals, with at least one microorganism of established respiratory pathogenicity identified in 113 (52.1%) of patients, and a microbe of possible pathogenicity identified in 94 (47.9%) of patients. Mycobacterium tuberculosis (MTB) was the most commonly identified established pathogen in 35 (16.1%) of the patients and bacterial or viral co-infections were found in 13 (37.2%) of MTB-positive individuals. Streptococcus mitis, not previously reported as a cause of pneumonia in patients with HIV, was the most commonly identified bacterial organism (n=37, 17.1% of patients), and Hemophilus influenzae was the most commonly identified established bacterial pathogen (n=20, 9.2% of patients). Pneumocystis jirovecii, Hemophilus influenza, human rhinovirus, Streptococcus species and Veillonella species were more prevalent in patients with a CD4 T-cell count of

The interaction between semiconductor materials and electromagnetic fields resonating in microcavities or the light-matter coupling is of both fundamental and practical significance for improving the performance of various photonic technologies. The demonstration of light-matter coupling effects in the emerging perovskite-based optoelectronic devices via optical pumping and electrical readout (e.g., photovoltaics) and vice versa (e.g., light-emitting diodes), however, is still scarce. Here, we demonstrate the microcavity formation in vacuum-deposited methylammonium lead iodide (CH3NH3PbI3, MAPI) p-i-n photovoltaic devices fabricated between two reflecting silver electrodes. We tune the position of the microcavity mode across MAPI's absorption edge and study the effect on the microcavity absorption enhancement. Tuning the microcavity mode toward lower energies enhances the absorption of the lower energy photons and steepens the absorption onset which reduces the effective optical gap (E-g) of the devices. This leads to a reduction in the open circuit voltage deficit. The research leading to these results has received funding from the Spanish Ministry of Science, Innovation and Universities (MICIU, RTI2018-095362-A-I00, PCI2019-111829-2, CEX2019-000919-M, and EQC2018-004888-P) and the Comunitat Valenciana (IDIFEDER/2018/061 and PROMETEU/2020/077). C.D. acknowledges that the project that gave rise to these results received the support of a fellowship from “la Caixa” Foundation (ID 100010434, code LCF/BQ/ DI19/11730020). M.S. acknowledges the MICIU for his RyC contract. A.P. acknowledges his Grisolia Grant from the Comunitat Valenciana GRISOLIAP/2020/134.

Herein, the preparation of fully vacuum-processed bismuth triiodide solar cells with low annealing temperature is reported. Planar n-i-p devices are prepared using a thin compact SnO2 layer as the electron extraction layer and an electron blocking/hole extraction bilayer consisting of an intrinsic and doped organic hole-transport molecule. Using this configuration, herein, higher fill-factors and overall power conversion efficiencies than with conventional solution-processed hole transport materials are achieved.

We use the framework of asymptotic safety above the Planck scale to constrain the parameter space of simple models of new physics that can accommodate the measured value of the anomalous magnetic moment of the muon and the relic density of dark matter. We couple parametrically to the trans-Planckian quantum physics a set of SU(2)$\times$U(1) invariant extensions of the Standard Model, each comprising an inert scalar field and one pair of colorless fermions that communicate to the muons through Yukawa-type interactions. The presence of an interactive UV fixed point in the system of gauge and Yukawa couplings imposes a set of boundary conditions at the Planck scale, which allow one to derive unique phenomenological predictions in each case and distinguish the different representations of the gauge group from one another. We apply to the models constraints from the $h\to \mu\mu$ signal strength at ATLAS and CMS, direct LHC searches for electroweak production with leptons and missing energy in the final state, and the dark matter relic density. We find that they further restrict the available parameter space., Comment: 40 pages, 7 figures, 7 tables. Updated with the new measurement of the muon g-2 at Fermilab. Added models M6 and M10. Added references

Physical theories that depend on many parameters or are tested against data from many different experiments pose unique challenges to statistical inference. Many models in particle physics, astrophysics and cosmology fall into one or both of these categories. These issues are often sidestepped with statistically unsound ad hoc methods, involving intersection of parameter intervals estimated by multiple experiments, and random or grid sampling of model parameters. Whilst these methods are easy to apply, they exhibit pathologies even in low-dimensional parameter spaces, and quickly become problematic to use and interpret in higher dimensions. In this article we give clear guidance for going beyond these procedures, suggesting where possible simple methods for performing statistically sound inference, and recommendations of readily-available software tools and standards that can assist in doing so. Our aim is to provide any physicists lacking comprehensive statistical training with recommendations for reaching correct scientific conclusions, with only a modest increase in analysis burden. Our examples can be reproduced with the code publicly available at https://doi.org/10.5281/zenodo.4322283., 15 pages, 4 figures. extended discussions. closely matches version accepted for publication

In a short period of time, the rapid development of perovskite solar cells attracted a lot of attention in the science community with the record for power conversion efficiency being broken every year. Despite the fast progress in power conversion efficiency there are still many issues that need to be solved before starting large scale commercial applications, such as, among others, the difficult and costly synthesis and usage of toxic solvents for the deposition of hole transport materials (HTMs). We herein report new enamine-based charge transport materials obtained via a simple one step synthesis procedure, from commercially available precursors and without the use of expensive organometallic catalysts. The developed materials demonstrated rapid loss of mass during thermogravimetry analysis suggesting that they could be processed not only using solution processing but also via vacuum deposition. Furthermore, all HTMs demonstrated high charge carrier mobility with H2 possessing the highest mobility of 2.5 × 10−2 cm2 V−1 s−1 under strong electric fields. The investigated materials were employed in vacuum-deposited p–i–n perovskite solar cells and champion devices with enamine H2 demonstrate a PCE of 18.4%.

Halide perovskites have generated considerable research interest due to their excellent optoelectronic properties in the past decade. To ensure the formation of high-quality semiconductors, the deposition process for the perovskite film is a critical issue. Vacuum-based processing is considered to be a promising method, allowing, in principle, for uniform deposition on a large area. One of the benefits of vacuum processing is the control over the film composition through the use of quartz crystal microbalances (QCMs) that monitor the rates of the components in situ. In metal halide perovskites, however, one frequently employed component or precursor, CH

A rigid dinuclear Ir(III) complex showing high photoluminescence quantum yield in pure films was successfully used to fabricate light-emitting electrochemical cells with and without ionic liquid additives. The devices showed nearly instantaneous electroluminescence after biasing and maximum quantum yield approaching 1%. The lifetime of the devices was found to be limited to approximately 20 hours, which we correlated with the irreversible oxidation of the complex as seen from electrochemical measurements. This work validates the use of highly luminescent dinuclear iridium complexes in light-emitting electrochemical cells. Future studies will pursue materials with more efficient photoluminescence as well as improved electrochemical stability.

Halide perovskites have shown excellent photophysical properties for solar cell applications which led to a rapid increase of the device efficiency. Understanding the charge carrier dynamics within the active perovskite absorber and at its interfaces will be key to further progress in their development. Here we present a series of fully evaporated devices employing hole transport materials with different ionization energies. The open circuit voltage of the devices, along with their ideality factors, confirm that the former is mainly determined by the bulk and surface recombination in the perovskite, rather than by the energetic offset between the valence band of the perovskite and the highest occupied molecular orbital of the organic transport layers. These results help to further understand the origin of the open circuit potential in perovskite solar cells, which is an important parameter that needs to be improved to further boost power conversion efficiencies.

We report herein a simple ligand-assisted reprecipitation method at room temperature to synthesize mixed-cation hybrid organic–inorganic perovskite nanocrystals with low structural dimensionality., We report herein a simple ligand-assisted reprecipitation method at room temperature to synthesize mixed-cation hybrid organic–inorganic perovskite nanocrystals with low structural dimensionality. The emission wavelength of iodide-based perovskites is thus tuned from the near-infrared to the red part of the visible spectrum. While this is mostly achieved in the literature by addition of bromide, we demonstrate here a controllable blueshift of the band gap by varying the chain length of the alkylammonium ligands. Furthermore, an antisolvent washing step was found to be crucial to purify the samples and obtain single-peak photoluminescence with a narrow linewidth. The so-formed nanocrystals exhibit high and stable photoluminescence quantum yields exceeding 90% over 500 hours, making these materials ideal for light-emitting applications.

Heteroleptic [Cu(P^P)(N^N)][PF

For the majority of biosensors or biomedical devices, immobilization of the biorecognition element is a critical step for device function. To achieve longer lifetime devices and controllable functionalization, covalent immobilisation techniques are preferred over passive adhesion and electrostatic interactions. The rapidly emerging field of organic bioelectronics uses conducting polymers (or small molecules) as the active materials for transduction of the biological signal to an electronic one. While a number of techniques have been utilized to entrap or functionalize conducting polymers deposited by electro- or vapor phase polymerization, covalent functionalization of solution processed films, essential for realizing low cost or high throughput fabrication, has not been thoroughly investigated. In this study we show a versatile biofunctionalization technique for the solution processable conducting polymer poly(3,4-ethylenedioxythiophene) doped with poly(styrenesulfonate) PEDOT:PSS, which is a commercially available material, and has a record high conductivity. Addition of poly(vinyl alcohol) (PVA) into the solution with PEDOT:PSS provides a handle for subsequent silanization with a well-characterised silane reagent, allowing for covalent linkage of biological moieties onto PEDOT:PSS films. We show homogenous and large-scale biofunctionalization with polypeptides and proteins, as well as maintenance of the biological functionalities of the proteins. In addition, no deleterious effects are noted on the electronic or ionic transport properties of the conducting polymer films due to incorporation of the PVA.

Chloride is extensively used in the preparation of metal halide perovskites such as methylammonium lead iodide (MAPbI(3-x)Cl(x)), but its persistence and role in solution-processed materials has not yet been rationalized. Multiple-source vacuum deposition of perovskites enables a fine control over thin-film stoichiometry and allows the incorporation of chemical species irrespective of their solubility. Herein, the first example of mixed MAPbI(3-x)Cl(x) thin films prepared by three-source vacuum deposition is presented using methylammonium iodide (MAI), PbI2, and PbCl2 as precursors. The optoelectronic properties of the material are evaluated through photovoltaic and electro-/photoluminescent characterizations. Besides the very similar structural and optical properties of MAPbI(3) and MAPbI(3-x)Cl(x), an increased electroluminescence efficiency, longer photoluminescence lifetimes, as well as larger photovoltage, are observed in the presence of chloride, suggesting a reduction of nonradiative charge recombination.

Conductive metal-organic frameworks are opening new perspectives for the use of these porous materials for applications traditionally limited to more classical inorganic materials, such as their integration into electronic devices. This has enabled the development of chemiresistive sensors capable of transducing the presence of specific guests into an electrical response with good selectivity and sensitivity. By combining experimental data with computational modelling, a possible origin for the underlying mechanism of this phenomenon in ultrathin films (ca. 30 nm) of Cu-CAT-1 is described. ispartof: ANGEWANDTE CHEMIE-INTERNATIONAL EDITION vol:57 issue:46 pages:15086-15090 ispartof: location:Germany status: published

Metal-halide perovskites have become the most studied material for efficient next-generation solar cells, in part because of the possibility of depositing high quality semiconducting perovskites by simple solution-based methods. However, the majority of solvent systems implemented in literature for deposition of lead halide perovskites are hazardous to handle. Investigation of alternatives perovskite processing methods are hence key to safely upscale the perovskite photovoltaic manufacturing. In this manuscript we use the Hansen theory to find suitable nonhazardous solvents to solubilize two lead salts, PbBr2 and PbI2, used to fabricate the corresponding methylammonium (MA) lead halide perovskite films. The method is based on the use of the Hansen solubility parameters (HSPs) of a lead salt and a solvent to provide insight into whether interactions between them are favorable or not. We first studied the solubility properties of each lead salt (PbBr2 and PbI2) by determining experimentally their Hansen solubility spheres. Using these results, computer simulations allow us to determine compatible nonhazardous solvents with these two compounds in terms of solubility. We further investigated the use of a nonhazardous diester blend polar solvent to deposit MAPbI3 and MAPbBr3 thin films.

“The Selfie Project” is the final assignment in an upper-level undergraduate course on writing with digital and social media. The assignment intends to increase students' awareness of their everyday practices by asking them to critically analyze the act of taking pictures of themselves. Selfies have become an integral part of students' daily lives. For example, students post selfies on social media, they take selfies at parties and on vacation, and they use them to connect with their communities. Though they might seem inconsequential, selfies are rhetorically rich sites of character presentation in the world of social media: practicing their composition offers students a novel way to enhance understanding of character presentation in social media. With this assignment, students successfully brainstorm, compose, and revise rhetorical content in a genre they are already culturally familiar with.

Funding: The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: MIND study was funded by National Institutes of Health (NIH) (NIH K24 HL087713, R01 HL090335, and R01 HL128156). MBN Clinical Laboratories provided PCR reagents, other laboratory consumables, and workspace. Sylvia Kaswabuli received a partial scholarship from the Pulmonary Complications of AIDS Research Training Program (NIH D43TW009607). Objective The objective of the study was to determine the diagnostic performance of the GenoQuick MTB test on heated sputum against the conventional Lowenstein–Jensen Mycobacterium tuberculosis culture as the reference method for tuberculosis diagnosis. Introduction Fast, reliable, and easy-to-use tests for tuberculosis diagnosis are essential to achieving the Sustainable Development Goal of diagnosing and treating 90% of tuberculosis patients by 2030. We evaluated the diagnostic performance of the GenoQuick MTB, a polymerase chain reaction–lateral flow test, in Uganda, a resource-constrained, high tuberculosis- and HIV-burden setting. Methods Fresh sputum samples from presumptive tuberculosis patients at Mulago Hospital were tested for M. tuberculosis using smear microscopy, GenoQuick MTB test, and Lowenstein–Jensen culture. For the GenoQuick MTB test, mycobacterial DNA was extracted by heating sputum at 95°C for 30 min while DNA amplification and detection were done following the manufacturer’s protocol (Hain Lifescience, Nehren, Germany). Sensitivity, specificity, and kappa agreements were calculated against Lowenstein–Jensen M. tuberculosis culture as a reference test using STATA V12. Results Of the 86 tested samples, 30.2% had culture-confirmed pulmonary tuberculosis. Overall, sensitivity was higher for GenoQuick MTB (81%, 95% confidence interval: 60%−93%) than for smear microscopy (69%, 95% confidence interval: 48%−86%). Among people living with HIV, sensitivity was identical for GenoQuick MTB and smear tests (75%, 95% confidence interval: 42%−95%). Contrastingly, smear had a higher overall specificity (98%, 95% confidence interval: 91%−100%) than for GenoQuick MTB (92%, 95% confidence interval: 81%−97%). A similar trend of specificity was observed among the people living with HIV for smear microscopy (100%, 95% CI: 87%−100%) and for GenoQuick MTB (96%, 95% confidence interval: 81%−100%). Conclusion The GenoQuick MTB test could be a potential tuberculosis diagnostic test given its higher sensitivity. Evaluation of this test in larger studies is recommended. Publisher PDF