Light Induced Increase of Electron Diffusion Length in a p n Junction Type CH3NH3PbBr3 Perovskite Solar Cell

High band gap, high open circuit voltage solar cells with methylammonium lead tribromide MAPbBr3 perovskite absorbers are of interest for spectral splitting and photoelectrochemical applications, because of their good performance and ease of processing. The physical origin of high performance in these and similar perovskite based devices remains only partially understood. Using cross sectional electron beaminduced current EBIC measurements, we find an increase in carrier diffusion length in MAPbBr3 Cl based solar cells upon low intensity a few percent of 1 sun intensity blue laser illumination. Comparing dark and illuminated conditions, the minority carrier electron diffusion length increases about 3.5 times from Ln 100 50 nm to 360 22 nm. The EBIC cross section profile indicates a p amp; 8722;n structure between the n FTO TiO2 and p perovskite, rather than the p amp; 8722;i amp; 8722;n structure, reported for the iodide derivative. On the basis of the variation in space charge region width with varying bias, measured by EBIC and capacitance amp; 8722;voltage measurements, we estimate the net doping concentration in MAPbBr3 Cl to be 3 amp; 8722;6 1017 cm amp; 8722;

Direct Probing of Gap States and Their Passivation in Halide Perovskites by High-Sensitivity, Variable Energy Ultraviolet Photoelectron Spectroscopy

Direct detection of intrinsic defects in halide perovskites (HaPs) by standard methods utilizing optical excitation is quite challenging, due to the low density of defects in most samples of this family of materials (≤10^{15} cm^{–3} in polycrystalline thin films and ≤10^{11} cm^{–3} in single crystals, except melt-grown ones). While several electrical methods can detect defect densities 2 eV) HaPs. By measuring HaP layers on both hole- and electron-contact layers, as well as single crystals without contacts, we conclude that the observed deep defects are intrinsic to the Br-based HaP, and we propose a passivation route via the incorporation of a 2D-forming ligand into the precursor solution

Low-Temperature Solution-Grown CsPbBr3_{3} Single Crystals and Their Characterization

Cesium lead bromide (CsPbBr$_{3}$) was recently introduced as a potentially high performance thin-film halide perovskite (HaP) material for optoelectronics, including photovoltaics, significantly more stable than MAPbBr$_{3}$ (MA = CH$_{3}$NH$_{3}$+). Because of the importance of single crystals to study relevant material properties per se, crystals grown under conditions comparable to those used for preparing thin films, i.e., low-temperature solution-based growth, are needed. We show here two simple ways, antisolvent-vapor saturation or heating a solution containing retrograde soluble CsPbBr$_{3}$, to grow single crystals of CsPbBr$_{3}$ from a precursor solution, treated with acetonitrile (MeCN) or methanol (MeOH). The precursor solutions are stable for at least several months. Millimeter-sized crystals are grown without crystal-seeding and can provide a 100% yield of CsPbBr$_{3}$ perovskite crystals, avoiding a CsBr-rich (or PbBr$_{2}$-rich) composition, which is often present alongside the perovskite phase. Further growth is demonstrated to be possible with crystal seeding. The crystals are characterized in several ways, including first results of charge carrier lifetime (30 ns) and an upper-limit of the Urbach energy (19 meV). As the crystals are grown from a polar aprotic solvent (DMSO), which is similar to those used to grow hybrid organic-inorganic HaP crystals, this may allow growing mixed (organic and inorganic) monovalent cation HaP crystals.G.H. and D.C. acknowledge the Israel Ministry of Science and the Israel National Nano-Initiative for partial support and G.H. acknowledges the Leona M. and Harry B. Helmsley Charitable Trust. A.S., M.L.B., and R.H.F. would like acknowledge EPSRC for their support. A.S. would also like to acknowledge support from an India-UK APEX project

Лечение критической ишемии на фоне многократных тромбозов бранши аорто-бедренного шунта и отсутствия дистального русла: 2 случая успешной гибридной реваскуляризации

Patients with CLI often present multilevel disease. They underwent multiply revascularization procedures aiming to save thelimb. The main obstacle is absence or poor outflow arteries. Inability to restore bloodflow usuallyleads to ischemia progression and consequent amputation. We describe two cases of successful treatment of patient with CLI after multiply ABF thrombosis and absence of outflow arteries.The first 63 years old patient developed the third case of ABF thrombosis as a result of profunda and superficial femoral arteries chronic occlusion. We performed mechanical recanalization and angioplasty of anterior tibial, popliteal, subintimal recanalization and angioplasty of superficial femoral arteries. After that the ABFleg was sutured to subintimal space of femoral artery. The next case was another 63 years old patient with total chronic occlusion of iliac, femoral, popliteal and tibioperoneal trunk. We performed mechanical recanalization and angioplasty of anterior tibial, popliteal, subintimal recanalization and angioplasty of superficial femoral arteries. And then extra anatomy femoro-femoral autovenous bypass, distal anastomosis was performed by using subintimal artery space also. Thelong term period was 27 months for the first case and 20 months - for the second one. All bypasses were patient.Therefore this described above approach of hybrid open and endovascular surgery could give additional chance forlowlimb revascularization in this so-called hopeless group with criticallimb ischemia.У пациентов с критической ишемией нижних конечностей почти всегда встречается многоуровневое поражение. Им многократно выполняются реконструкции магистральных артерий с целью сохранения пораженной конечности. Основным лимитирующим фактором выполнения подобных операций является отсутствие принимающего сосудистого русла - т. н. путей оттока. Невозможность проведения повторной реваскуляризации конечности обычно приводит к прогрессированию ишемии и ампутации конечности. Представляем 2 случая успешного гибридного лечения пациентов с критической ишемией конечности на фоне тотальной окклюзии артерий (подвздошных и бедренных, в т. ч. и глубокой артерии бедра) после неоднократных попыток открытых операций. Первый пациент, 63 лет, перенес третий по счету тромбоз бранши аорто-бедренного протеза на фоне окклюзии ствола глубокой бедренной артерии и облитерации поверхностной бедренной артерии. Были выполнены механическая реканализация и ангиопластика передней берцовой, подколенной артерий, субинтимальная реканализация и ангиопластика поверхностной бедренной артерии, и бранша аорто-бедренного протеза после тромбэктомии анастомозирована с субинтимальным пространством артерии. У второго пациента, тоже 63 лет, была диагностирована тотальная окклюзия общей наружной подвздошных, общей поверхностной и глубокой бедренных, подколенной артерий и тибиоперонеального ствола. После предварительной механической реканализации и ангиопластики передней берцовой подколенной артерий, субинтимальной реканализации и ангиопластики поверхностной бедренной артерии было выполнено перекрестное аутовенозное бедренно-бедренное шунтирование, при этом дистальный анастомоз перекрестного шунта анастомозирован с субинтимальным пространством поверхностной бедренной артерии. Через 27 мес. после первой операции и 20 мес. - после второй у обоих больных шунты были проходимы, конечности сохранены, болевого синдрома и трофических расстройств не было. Использование сочетания открытой и эндоваскулярной хирургии, возможность анастомозирования сосудов даже после проведенной субинтимальной реканализации и с субинтимальным пространством дает дополнительные возможности для реваскуляризации конечности у такой, казалось бы, безнадежной группы больных критической ишемией конечности

Direct Probing of Gap States and Their Passivation in Halide Perovskites by High Sensitivity, Variable Energy Ultraviolet Photoelectron Spectroscopy

Direct detection of intrinsic defects in halide perovskites (HaPs) by standard methods utilizing optical excitation is quite challenging, due to the low density of defects in most samples of this family of materials (≤10^{15} cm^{–3} in polycrystalline thin films and ≤10^{11} cm^{–3} in single crystals, except melt-grown ones). While several electrical methods can detect defect densities 2 eV) HaPs. By measuring HaP layers on both hole- and electron-contact layers, as well as single crystals without contacts, we conclude that the observed deep defects are intrinsic to the Br-based HaP, and we propose a passivation route via the incorporation of a 2D-forming ligand into the precursor solution

Graphite-protected CsPbBr3 perovskite photoanodes functionalised with water oxidation catalyst for oxygen evolution in water

Metal-halide perovskites have been widely investigated in the photovoltaic sector due to their promising optoelectronic properties and inexpensive fabrication techniques based on solution processing. Here we report the development of inorganic CsPbBr3-based photoanodes for direct photoelectrochemical oxygen evolution from aqueous electrolytes. We use a commercial thermal graphite sheet and a mesoporous carbon scaffold to encapsulate CsPbBr3 as an inexpensive and efficient protection strategy. We achieve a record stability of 30 h in aqueous electrolyte under constant simulated solar illumination, with currents above 2 mA cm−2 at 1.23 VRHE. We further demonstrate the versatility of our approach by grafting a molecular Ir-based water oxidation catalyst on the electrolyte-facing surface of the sealing graphite sheet, which cathodically shifts the onset potential of the composite photoanode due to accelerated charge transfer. These results suggest an efficient route to develop stable halide perovskite based electrodes for photoelectrochemical solar fuel generation

Deep Defect States in Wide Band Gap ABX 3 Halide Perovskites

We find 4 different deep defect states in polycrystalline layers of mixed cation lead tribromide from high sensitivity modulated surface photovoltage SPV spectroscopy. Measurements were performed with different contact configurations, on complete solar cells and on samples before and after aging or stressing at 85 C under illumination. Three of the four states, with energies of 0.63, 0.73 and 1.35 eV below the conduction band edge, are assigned to intrinsic defects whereas defect states in the middle of the band gap are thought to be associated with uncontrolled impuritie

Light-Induced Increase of Electron Diffusion Length in a p–n Junction Type CH₃NH₃PbBr₃ Perovskite Solar Cell

High band gap, high open-circuit voltage solar cells with methylammonium lead tribromide (MAPbBr₃) perovskite absorbers are of interest for spectral splitting and photoelectrochemical applications, because of their good performance and ease of processing. The physical origin of high performance in these and similar perovskite-based devices remains only partially understood. Using cross-sectional electron-beam-induced current (EBIC) measurements, we find an increase in carrier diffusion length in MAPbBr₃(Cl)-based solar cells upon low intensity (a few percent of 1 sun intensity) blue laser illumination. Comparing dark and illuminated conditions, the minority carrier (electron) diffusion length increases about 3.5 times from <i>L</i>_n = 100 ± 50 nm to 360 ± 22 nm. The EBIC cross section profile indicates a p–n structure between the n-FTO/TiO₂ and p-perovskite, rather than the p–i–n structure, reported for the iodide derivative. On the basis of the variation in space-charge region width with varying bias, measured by EBIC and capacitance–voltage measurements, we estimate the net-doping concentration in MAPbBr₃(Cl) to be 3–6 × 10¹⁷ cm^–3

Atrial Substrate and Triggers of Paroxysmal Atrial Fibrillation in Patients With Obstructive Sleep Apnea

Obstructive sleep apnea (OSA) is associated with atrial remodeling, atrial fibrillation (AF), and increased incidence of arrhythmia recurrence after pulmonary vein (PV) isolation. We aimed to characterize the atrial substrate, including AF triggers in patients with paroxysmal AF and OSA. In 86 patients with paroxysmal AF (43 with ≥moderate OSA [apnea-hypopnea index ≥15] and 43 without OSA [apnea-hypopnea index <5]), right atrial and left atrial voltage distribution, conduction velocities, and electrogram characteristics were analyzed during atrial pacing. AF triggers were examined before and after PV isolation and targeted for ablation. Patients with OSA had lower atrial voltage amplitude (right atrial, =0.0005; left atrial, =0.0001), slower conduction velocities (right atrial, =0.02; left atrial, =0.0002), and higher prevalence of electrogram fractionation ( =0.0001). The areas of atrial abnormality were consistent among patients, most commonly involving the left atrial septum (32/43; 74.4%). At baseline, the PVs were the most frequent triggers for AF in both groups; however, after PV isolation patients with OSA had increased incidence of additional extra-PV triggers (41.8% versus 11.6%; =0.003). The 1-year arrhythmia-free survival was similar between patients with and without OSA (83.7% and 81.4%, respectively; =0.59). In comparison, control patients with paroxysmal AF and OSA who underwent PV isolation alone without ablation on extra-PV triggers had increased risk of arrhythmia recurrence (83.7% versus 64.0%; =0.003). OSA is associated with structural and functional atrial remodeling and increased incidence of extra-PV triggers. Elimination of these triggers resulted in improved arrhythmia-free survival