Status of the FETS Project

The Front End Test Stand (FETS) under construction at RAL is a demonstrator for front end systems of a future high power proton linac. Possible applications include a linac upgrade for the ISIS spallation neutron source, new future neutron sources, accelerator driven sub-critical systems, high energy physics proton drivers etc. Designed to deliver a 60mA H-minus beam at 3MeV with a 10% duty factor, FETS consists of a high brightness ion source, magnetic low energy beam transport (LEBT), 4-vane 324MHz radio frequency quadrupole, medium energy beam transport (MEBT) containing a high speed beam chopper and non-destructive laser diagnostics. This paper describes the current status of the project and future plans

Photon recycling in lead iodide perovskite solar cells.

Lead-halide perovskites have emerged as high-performance photovoltaic materials. We mapped the propagation of photogenerated luminescence and charges from a local photoexcitation spot in thin films of lead tri-iodide perovskites. We observed light emission at distances of ≥50 micrometers and found that the peak of the internal photon spectrum red-shifts from 765 to ≥800 nanometers. We used a lateral-contact solar cell with selective electron- and hole-collecting contacts and observed that charge extraction for photoexcitation >50 micrometers away from the contacts arose from repeated recycling between photons and electron-hole pairs. Thus, energy transport is not limited by diffusive charge transport but can occur over long distances through multiple absorption-diffusion-emission events. This process creates high excitation densities within the perovskite layer and allows high open-circuit voltages.The authors acknowledge financial support from the Engineering and Physical Sciences Research Council of the UK (EPSRC) and King Abdulaziz City for Science and Technology (KACST). L.M.P.O. and H.J.B. also thank the Nano doctoral training center (NanoDTC) for financial support. M.S., M.V. and J.M.R. thank the Winton programme for the physics of sustainability. M.C.Q would like to thank the Marie Curie Actions (FP7-PEOPLE-IEF2013) for funding. M.A.J. thanks Nyak Technology Ltd for PhD scholarship and B.E. acknowledges the Foundation for Fundamental Research on Matter (FOM), which is part of the Netherlands Organization for Scientific Research (NWO). F.D. acknowledges funding through a Herchel Smith Research Fellowship. We acknowledge Prof. Henning Sirringhaus, Prof. Neil Greenham, Prof. Ullrich Steiner, Dr. Erwin Reisner and Prof. Richard Phillips for providing support and access to their facilities.This is the author accepted manuscript. The final version is available from the American Association for the Advancement of Science via http://dx.doi.org/10.1126/science.aaf116

Local Strain Heterogeneity Influences the Optoelectronic Properties of Halide Perovskites

Halide perovskites are promising semiconductors for optoelectronics, yet thin films show substantial microscale heterogeneity. Understanding the origins of these variations is essential for mitigating parasitic losses such as non-radiative decay. Here, we probe the structural and chemical origins of the heterogeneity by utilizing scanning X-ray diffraction beamlines at two different synchrotrons combined with high-resolution transmission electron microscopy to spatially characterize the crystallographic properties of individual micrometer-sized perovskite grains in high-quality films. We reveal new levels of heterogeneity on the ten-micrometer scale (super-grains) and even ten-nanometer scale (sub-grain domains). By directly correlating these properties with their corresponding local time-resolved photoluminescence properties, we find that regions showing the greatest luminescence losses correspond to strained regions, which arise from enhanced defect concentrations. Our work reveals remarkably complex heterogeneity across multiple length scales, shedding new light on the defect tolerance of perovskites

Perceptions and Attitudes Towards HIV/AIDS Patients among General Public in Bahrain

Introduction: HIV/AIDS is a major global health problem. In Bahrain, although the prevalence of HIV is low, awareness programs are of high importance for controlling and preventing the distribution of HIV infection. The aim of this study is to determine the attitudes and risk perceptions toward HIV/AIDS in Bahrain. Results of this study will provide background knowledge to inform existing and new educational and preventiveprograms. Methodology: A self-administered questionnaire-based survey was conducted among 1038 Bahraini adults. Results: The study showed varied attitudes toward HIV/AIDS, but mostly were negative, as 60% of participants agreed to isolate HIV/AIDS patients in workplaces and schools, and 52.4% of them believed that HIV is a divine punishment. A high proportion of respondents (84.4%) believed that religion plays an important role in minimizing the spread of the disease. Conclusions: The Bahraini public negative attitudes toward HIV/AIDS was a major finding of this study. Successful control programs of HIV infection require limiting the negative attitudes toward HIV patients and the disease. Those negative attitudes found in this study need to be addressed through new and currently existing education and health awareness programs in Bahrain. Keywords: HIV/AIDS, Public Attitudes, Stigmatization, Bahrai

Back-Contact Perovskite Solar Cells

Interdigitated back-contact (IBC) architectures are the best performing technology in crystalline Si (c-Si) photovoltaics (PV). Although single junction perovskite solar cells have now surpassed 23% efficiency, most of the research has mainly focussed on planar and mesostructured architectures. The number of studies involving IBC devices is still limited and the proposed architectures are unfeasible for large scale manufacturing. Here we discuss the importance of IBC solar cells as a powerful tool for investigating the fundamental working mechanisms of perovskite materials. We show a detailed fabrication protocol for IBC perovskite devices that does not involve photolithography and metal evaporation. The interview is available at https://youtu.be/nvuNC29TvOY.The authors thank the Engineering and Physical Sciences Research Council (EPSRC). XMaS is a mid-range facility supported by the EPSRC. The authors also thank all the XMaS beamline team staff for their support. M.A.-J. thanks Cambridge Materials Limited and EPSRC (EP/M005143/1) for their funding and technical support. M.A. acknowledges support from the President of the UAE’s Distinguished Student Scholarship Program (DSS), granted by the UAE’s Ministry of Presidential Affairs

Impact of A-Site Cation Modification on Charge Transport Properties of Lead Halide Perovskite for Photovoltaics Applications

Perovskite solar cells (PSCs) have reached a formidable power conversion efficiency of 25.7% over the years of development. One of the strategies that has been responsible for the development of stable and highly efficient PSCs is modifications of the monovalent A-site cations (methylammonium, MA; formamidinium, FA; cesium, Cs, etc.) in lead halide perovskites. Herein, the impact of modifying the monovalent cation (MA, FAMA, CsFAMA, potassium-passivated CsFAMA, rubidium-passivated CsFAMA) in lead halide perovskite on their optoelectronic, charge transport, and photovoltaic behavior is systematically studied. Reduced trap density and improved charge carrier mobility after introduction of FA and Cs in the MAPb(I0.85Br0.15)3 system are confirmed. Further passivation of the triple-cation perovskite with K and Rb enhances the optoelectronic characteristics, charge transport, and charge extraction efficiency in halide perovskite solar cells

Grain rotation and lattice deformation during perovskite spray coating and annealing probed in situ by GI-WAXS

We report for the first time on grain rotation in CH3NH3PbI3 perovskite films for ∼12% efficient planar solar cells and present a new method for investigating their texture evolution during thermal annealing. Our technique is based on in situ 2D grazing incidence wide-angle X-ray scattering (GI-WAXS) and employs a 10 keV wide-focussed X-ray beam to simultaneously probe a large number of grains. The ability to track the texture dynamics from a statistically relevant number of spots diffracting from single grains during thermal annealing and in grazing incidence geometry can have applications understanding the processing dynamics of a range of new materials

Can the conventional cytology technique be sufficient in a center lacking ROSE?: Retrospective study during the COVID-19 pandemic

While rapid on-site evaluation (ROSE) is considered to be an additional tool to optimize the yield of tissue acquisition during EUS-guided FNA of the gastrointestinal tract (1)(2) it is not readily available at all times while performing these procedures. We reviewed twenty-seven EUS-guided FNA procedures done at our institution in Tripoli central hospital with general working center restrictions due to local COVID-19 prevention protocols. Approximately 92.6 % of tissue adequacy was achieved despite the lack of ROSE which is comparable to ROSE-based tissue acquisition results. This is a small size retrospective chart review study to illustrate the optimal tissue adequacy during EUS-guided FNA of the upper gastrointestinal tract in a suboptimal hospital setting, lack of ROSE and merely utilizing visual inspection of those specimens by the performing physician and its effects on the diagnosis

Degradation Kinetics of Inverted Perovskite Solar Cells

We explore the degradation behaviour under continuous illumination and direct oxygen exposure of inverted unencapsulated formamidinium(FA)0.83Cs0.17Pb(I0.8Br0.2)3, CH3NH3PbI3, and CH3NH3PbI3-xClx perovskite solar cells. We continuously test the devices in-situ and in-operando with current-voltage sweeps, transient photocurrent, and transient photovoltage measurements, and find that degradation in the CH3NH3PbI3-xClx solar cells due to oxygen exposure occurs over shorter timescales than FA0.83Cs0.17Pb(I0.8Br0.2)3 mixed-cation devices. We attribute these oxygen-induced losses in the power conversion efficiencies to the formation of electron traps within the perovskite photoactive layer. Our results highlight that the formamidinium-caesium mixed-cation perovskites are much less sensitive to oxygen-induced degradation than the methylammonium-based perovskite cells, and that further improvements in perovskite solar cell stability should focus on the mitigation of trap generation during ageing