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Developing multijunction perovskite solar cells (PSCs) is an attractive route to boost PSC efficiencies to above the single-junction Shockley-Queisser limit. However, commonly used tin-based narrow-bandgap perovskites have shorter carrier diffusion lengths and lower absorption coefficient than lead-based perovskites, limiting the efficiency of perovskite-perovskite tandem solar cells. In this work, we discover that the charge collection efficiency in tin-based PSCs is limited by a short diffusion length of electrons. Adding 0.03 molar percent of cadmium ions into tin-perovskite precursors reduce the background free hole concentration and electron trap density, yielding a long electron diffusion length of 2.72 ± 0.15 µm. It increases the optimized thickness of narrow-bandgap perovskite films to 1000 nm, yielding exceptional stabilized efficiencies of 20.2 and 22.7% for single junction narrow-bandgap PSCs and monolithic perovskite-perovskite tandem cells, respectively. This work provides a promising method to enhance the optoelectronic properties of narrow-bandgap perovskites and unleash the potential of perovskite-perovskite tandem solar cells. Tin-based perovskites possess the suitable narrow-bandgap for tandem solar cells but their short carrier diffusion lengths limit device efficiency. Here Yang et al . add cadmium ions to increase diffusion length to above 2 µm by reducing the background free hole concentration and electron trap density.

Identifying the origin of intrinsic instability for organic–inorganic halide perovskites (OIHPs) is crucial for their application in electronic devices, including solar cells, photodetectors, radiation detectors, and light-emitting diodes, as their efficiencies or sensitivities have already been demonstrated to be competitive with commercial available devices. Here we show that free charges in OIHPs, whether generated by incident light or by current-injection from electrodes, can reduce their stability, while efficient charge extraction effectively stabilizes the perovskite materials. The excess of both holes and electrons reduce the activation energy for ion migration within OIHPs, accelerating the degradation of OIHPs, while the excess holes and electrons facilitate the migration of cations or anions, respectively. OIHP solar cells capable of efficient charge-carrier extraction show improved light stability under regular operation conditions compared to an open-circuit condition where the photo-generated charges are confined in the perovskite layers. Optoelectronic devices based on organic–inorganic halide perovskites show promising performance, but their poor stability impedes the commercialization. Here Lin et al. show that excess free charges are detrimental and efficient charge-carrier extraction is necessary for improved device stability.

The efficiencies of green and red perovskite light-emitting diodes (PeLEDs) have been increased close to their theoretical upper limit, while the efficiency of blue PeLEDs is lagging far behind. Here we report enhancing the efficiency of sky-blue PeLEDs by overcoming a major hurdle of low photoluminescence quantum efficiency in wide-bandgap perovskites. Blending phenylethylammonium chloride into cesium lead halide perovskites yields a mixture of two-dimensional and three-dimensional perovskites, which enhances photoluminescence quantum efficiency from 1.1% to 19.8%. Adding yttrium (III) chloride into the mixture further enhances photoluminescence quantum efficiency to 49.7%. Yttrium is found to incorporate into the three-dimensional perovskite grain, while it is still rich at grain boundaries and surfaces. The yttrium on grain surface increases the bandgap of grain shell, which confines the charge carriers inside grains for efficient radiative recombination. Record efficiencies of 11.0% and 4.8% were obtained in sky-blue and blue PeLEDs, respectively. Despite the rapid progress on perovskite light emitting diodes (PeLEDs), the efficiency of blue PeLEDs is lagging behind. Here Wang et al. employ yttrium (III) chloride additive to yield enhanced photoluminescence in the perovskite materials and thus record high device efficiencies for sky-blue and blue PeLEDs.

Ferroelasticity represents material domains possessing spontaneous strain that can be switched by external stress. Three-dimensional perovskites like methylammonium lead iodide are determined to be ferroelastic. Layered perovskites have been applied in optoelectronic devices with outstanding performance. However, the understanding of lattice strain and ferroelasticity in layered perovskites is still lacking. Here, using the in-situ observation of switching domains in layered perovskite single crystals under external strain, we discover the evidence of ferroelasticity in layered perovskites with layer number more than one, while the perovskites with single octahedra layer do not show ferroelasticity. Density functional theory calculation shows that ferroelasticity in layered perovskites originates from the distortion of inorganic octahedra resulting from the rotation of aspherical methylammonium cations. The absence of methylammonium cations in single layer perovskite accounts for the lack of ferroelasticity. These ferroelastic domains do not induce non-radiative recombination or reduce the photoluminescence quantum yield. Ruddlesden popper layered perovskites can be used in optoelectronic devices, but the understanding of their lattice strain as well as ferroelasticity is still lacking. Here, the authors find ferroelasticity in layered perovskites with layer number more than one and reveal its mechanism.

Background Hypertension is more prevalent and clinically severe among African–Americans than whites. Several health behaviors influence blood pressure (BP) control, but effective, accessible, culturally sensitive interventions that target multiple behaviors are lacking. Purpose We evaluated a culturally adapted, automated telephone system to help hypertensive, urban African–American adults improve their adherence to their antihypertensive medication regimen and to evidence-based guidelines for dietary behavior and physical activity. Methods We randomized 337 hypertensive primary care patients to an 8-month automated, multi-behavior intervention or to an education-only control. Medication adherence, diet, physical activity, and BP were assessed at baseline and every 4 months for 1 year. Data were analyzed using longitudinal modeling. Results The intervention was associated with improvements in a measure of overall diet quality (+3.5 points, p  < 0.03) and in energy expenditure (+80 kcal/day, p  < 0.03). A decrease in systolic BP between groups was not statistically significant (−2.3 mmHg, p  = 0.25). Conclusions Given their convenience, scalability, and ability to deliver tailored messages, automated telecommunications systems can promote self-management of diet and energy balance in urban African–Americans.

In the race to secure a renewable energy future, a variety of approaches to harness the power of sunlight have garnered significant research efforts. Semiconductors materials and devices have asserted themselves as a centerpiece in many approaches for harvesting solar energy, the most notable of which being photovoltaic and solar fuel applications. In both cases, the understanding and optimization of semiconductor material properties is paramount for the successful commercialization of next generation energy technologies. The performance of semiconductors is often challenged by the impact of material defects and resulting defect-induced trap states. In this dissertation, the characterization of material defects informs rational defect passivation of perovskite and tantalum nitride thin films for photovoltaic and solar fuel applications, respectively.State-of-the-art, high-performance perovskite solar cells (PSCs) contain a large amount of iodine to realize smaller bandgaps. However, the presence of numerous iodine vacancies at the surface of the film has been broadly shown to induce deep-level defects which limit the efficiency and stability of PSCs. In Chapter 2, modifying the defective surface of perovskite films with cadmium iodide (CdI2) effectively reduces the degree of surface iodine deficiency, and stabilizes iodine ions via the formation of strong Cd-I ionic bonds. This largely reduces the interfacial charge recombination loss, yielding a high efficiency of 21.9% for blade-coated PSCs with an open-circuit voltage of 1.20 V, corresponding to a record small voltage deficit of 0.31 V. The CdI2 surface treatment also improves the operational stability of the PSCs, retaining 92% efficiency after constant illumination at 1 sun intensity for 1000 h. This work provides a promising strategy to optimize the surface/interface optoelectronic properties of perovskites for more efficient and stable solar cells and other optoelectronic devices.Tantalum nitride (Ta3N5) has gained significant attention as a potential photoanode material; however, electrochemical performance and stability are challenged by high densities of defects and related trap states. Passivation of such defects has provided an enormous boost to the development of many semiconductor materials, particularly perovskites, but the understanding of defects and passivation thereof is still in its infancy for Ta3N5 materials and thin films. Utilizing drive-level capacitance profiling (DLCP) we reveal the spatial and energetic distribution of trap states throughout Ta3N5 thin films. Coupling DLCP with compositional and structural characterization we were able to attribute the high density of deep traps at surface of films to oxygen-related defects. This understanding informed our rational passivation via silatrane moieties capable of targeting the oxidized surface and ultimately suppressing trap density at the surface by two orders of magnitude and reducing free-carrier density of films by over one order of magnitude. The successful passivation of Ta3N5 films mitigates defect-induced charge trapping and recombination to ultimately improve material and device performance. Overall, the work reported in this dissertation demonstrates how detailed characterization and understanding of semiconductor thin films can be used to design rational passivation strategies capable of boosting material performance and stability and enable next-generation renewable technologies.

•DTaP5-HB-IPV-Hib is a vaccine against diseases caused by 6 infectious agents.•DTaP5-HB-IPV-Hib was given with 1 of 2 meningococcus group C conjugate vaccines.•Satisfactory seroprotection rates were achieved against all vaccine antigens.•High rates of seroprotection against meningococcus group C were observed. Concomitant administration of vaccines simplifies delivery. DTaP5-HB-IPV-Hib is a fully liquid, combination vaccine against 6 diseases. This study evaluated the compatibility of DTaP5-HB-IPV-Hib with 2 different meningococcus group C conjugate (MCC) vaccines in infants. In a phase 3, open-label study, 284 healthy infants from 11 UK centres received DTaP5-HB-IPV-Hib at age 2, 3, and 4 months; 13-valent pneumococcal conjugate vaccine (PCV13) at 2 and 4 months; a Haemophilus influenzae type b (Hib)-MCC vaccine and a measles/mumps/rubella vaccine at 12 months. Participants were randomised 1:1 to receive either an MCC-detoxified tetanus toxin vaccine (MCC-TT; n = 141) or an MCC-Corynebacterium diphtheriae CRM197 protein vaccine (MCC-CRM; n = 143) at 3 and 4 months. The primary outcome was seroprotection rate (SPR) to MCC (percent with rabbit complement serum bactericidal antibody titer ≥8). Per protocol analysis, MCC SPRs were 100 and 96.4 one month after the first dose, 100 and 99.1 after the second dose, and 100 and 97.3 after the third (booster) dose of MCC in the MCC-TT and MCC-CRM groups, respectively. One month after all 3 doses of DTaP5-HB-IPV-Hib, immunoglobulin G anti-polyribosylribitol phosphate SPRs (% ≥0.15 µg/mL) were 97.8 in the MCC-TT group and 100 in the MCC-CRM group; anti-hepatitis B antigen SPRs (% ≥10 mIU/mL) were 96.8 and 96.3 in the MCC-TT and MCC-CRM groups, respectively. All participants were seroprotected against diphtheria and tetanus (≥0.01 IU/mL) and poliovirus types 1, 2, and 3 (≥8 dilution), and seroresponse rates to all pertussis antigens were ≥90.4%. Two vaccine-related serious adverse events (transient severe abdominal pain and crying) occurred concomitantly in 1 participant in the MCC-CRM group. Adverse event rates were similar to other studies of DTaP5-HB-IPV-Hib, with pyrexia ≥38 °C in 10.9% of participants following any dose. DTaP5-HB-IPV-Hib can be effectively used in a 2-, 3-, and 4-month infant priming schedule when given with 2 doses of MCC.

After senior house officer posts in Sheffield, Leeds, Oxford, and London, Jenny completed her paediatric training in Nottingham (where she completed an MD) and Oxford before taking up her consultant post in Bath in 1992. Predeceased by her mother and oldest brother, she leaves her father; two sisters, one of whom, Pippa, is a professor of stroke medicine; and two brothers.

The Bath Clinical Ethics Committee (CEC) was launched in the autumn of 1999. The chairman, with a pre-existing interest in bioethics and aware of committees in Nottingham, Oxford, and the US, arranged a grand round to discuss two cases where particularly difficult ethical problems had arisen, and it was proposed that a CEC be established. One aspect of clinical governance with which the CEC is involved relates to do-not-attempt-resuscitation orders (DNAR), ensuring that they are implemented and are adhered to by all members of medical staff. The committee meets on a quarterly basis but other meetings have been held to discuss particular cases. The committee has three main roles: 1. to provide expert advice for particularly difficult ethical problems, 2. to ensure that policies within the hospital are sensitive to the needs of patients, and 3. to provide education in ethics to those working in the hospital. Examples illustrating the range of cases or issues recently referred to the committee are presented.