Oxygen doping-induced photogeneration loss in P3HT:PCBM solar cells

This work investigates the loss in performance induced by molecular oxygen in bulk heterojunction solar cells. We observe that upon exposure to molecular oxygen both formation of P3HT+:O2− complex and metal oxidation at the interface between the active layer and metallic contact occur. These two different effects were separately investigated using NOBF4 as an oxidant. Our procedure has allowed studying p-doping of the active layer independently from contact degradation. A loss in photocurrent is associated with formation of P3HT+:O2− complex, which reduces the concentration of neutral P3HT present in the film in accordance with absorption and external quantum efficiency spectra. This complex is regarded as a source of a pathway of reversible degradation. Capacitance–voltage measurements allow for an accurate extraction of p-doping levels of the active layer produced by the presence of charged O2− species. In addition, one of the irreversible degradation pathways is identified to be oxidation of the metallic contact to form CaO. This oxide forms a thin dipole layer producing a voltage drop across the active layer/Ca interface, which has a direct impact on the open circuit voltage and fill factor

How the Charge-Neutrality Level of Interface States Controls Energy Level Alignment in Cathode Contacts of Organic Bulk-Heterojunction Solar Cells

Electronic equilibration at the metal–organic interface, leading to equalization of the Fermi levels, is a key process in organic optoelectronic devices. How the energy levels are set across the interface determines carrier extraction at the contact and also limits the achievable open-circuit voltage under illumination. Here, we report an extensive investigation of the cathode energy equilibration of organic bulk-heterojunction solar cells. We show that the potential to balance the mismatch between the cathode metal and the organic layer Fermi levels is divided into two contributions: spatially extended band bending in the organic bulk and voltage drop at the interface dipole layer caused by a net charge transfer. We scan the operation of the cathode under a varied set of conditions, using metals of different work functions in the range of 2 eV, different fullerene acceptors, and several cathode interlayers. The measurements allow us to locate the charge-neutrality level within the interface density of sates and calculate the corresponding dipole layer strength. The dipole layer withstands a large part of the total Fermi level mismatch when the polymer:fullerene blend ratio approaches 1:1, producing the practical alignment between the metal Fermi level and the charge-neutrality level. Origin of the interface states is linked with fullerene reduced molecules covering the metal contact. The dipole contribution, and consequently the band bending, is highly sensitive to the nature and amount of fullerene molecules forming the interface density of states. Our analysis provides a detailed picture of the evolution of the potentials in the bulk and the interface of the solar cell when forward voltage is applied or when photogeneration takes place

Jet nebulizer-spray coated CZTS film as Pt-free electrocatalyst in photoelectrocatalytic fuel cells

The copper zinc tin sulphide (CZTS) is a promising p-type earth abundant alloy that received profound attention as an electron driven dark catalyst in electrocatalytic reduction reactions. In particular, the photoelectrocatalysis based solar fuel cell encompass with inexpensive electrocatalyst (hydrogen evolution reaction) is anticipated to support to reduce the overall system cost. However, demonstrating CZTS as Pt-free counter electrode in photoelectrocatalytic fuel cells is scarce. Because, achieving high electronic conductivity, favourable (1 1 2) crystalline structure towards high electrocatalytic property through low cost vacuum-free technique is remains challenge. In this report, we demonstrate p-type CZTS film fabrication at different processing temperature (250, 300, and 350 °C) using jet nebulizer spray (JNS) coating technique. The processing temperature play a key role on crystalline property, composition, and catalytic activity of CZTS. The x-ray diffraction and energy dispersive analysis results reveals that the CZTS film prepared 250 °C exhibit kesterite structure oriented in (1 1 2) direction. The electrocatalytic reduction property of as-synthesised CZTS electrodes in water reduction process is tested in aqueous 1 M NaOH solution. Among the different temperature processed films, CZTS prepared at 250 °C result high electrocatalytic reduction activity ∼-2.1 mA cm−2 at -0.44 V vs Ag/AgCl. In addition, these film exhibits high electrical conductivity than that of other CZTS samples. Therefore, optimised CZTS 250 °C film is further examined in hydrogen peroxide (H2O2) reduction which result enhanced electrical current generation after adding the 1 M of hydrogen peroxide in PBS electrolyte based electrochemical cell. This encouraged to apply as Pt-free counter electrode in H2O2 electrolyte based photoelectrocatalytic fuel cells. The PEC cells encompass with TiO2 nanowire photoelectrode, and CZTS-250 °C counter electrode showed feasible photocurrent generation compared to conventional Pt counter electrode. This proof-of-concept type Pt-free PEC cells leads to open new paths in implementing wide-range of semiconductor based electrocatalyst to support in development of low-cost photoelectrocatalytic fuel cells

Long-term adaptation following influenza A virus host shifts results in increased within-host viral fitness due to higher replication rates, broader dissemination within the respiratory epithelium and reduced tissue damage

The mechanisms and consequences of genome evolution on viral fitness following host shifts are poorly understood. In addition, viral fitness -the ability of an organism to reproduce and survive- is multifactorial and thus difficult to quantify. Influenza A viruses (IAVs) circulate broadly among wild birds and have jumped into and become endemic in multiple mammalian hosts, including humans, pigs, dogs, seals, and horses. H3N8 equine influenza virus (EIV) is an endemic virus of horses that originated in birds and has been circulating uninterruptedly in equine populations since the early 1960s. Here, we used EIV to quantify changes in infection phenotype associated to viral fitness due to genome-wide changes acquired during long-term adaptation. We performed experimental infections of two mammalian cell lines and equine tracheal explants using the earliest H3N8 EIV isolated (A/equine/Uruguay/63 [EIV/63]), and A/equine/Ohio/2003 (EIV/2003), a monophyletic descendant of EIV/63 isolated 40 years after the emergence of H3N8 EIV. We show that EIV/2003 exhibits increased resistance to interferon, enhanced viral replication, and a more efficient cell-to-cell spread in cells and tissues. Transcriptomics analyses revealed virus-specific responses to each virus, mainly affecting host immunity and inflammation. Image analyses of infected equine respiratory explants showed that despite replicating at higher levels and spreading over larger areas of the respiratory epithelium, EIV/2003 induced milder lesions compared to EIV/63, suggesting that adaptation led to reduced tissue pathogenicity. Our results reveal previously unknown links between virus genotype and the host response to infection, providing new insights on the relationship between virus evolution and fitness

Effect of angiotensin-converting enzyme inhibitor and angiotensin receptor blocker initiation on organ support-free days in patients hospitalized with COVID-19

IMPORTANCE Overactivation of the renin-angiotensin system (RAS) may contribute to poor clinical outcomes in patients with COVID-19. Objective To determine whether angiotensin-converting enzyme (ACE) inhibitor or angiotensin receptor blocker (ARB) initiation improves outcomes in patients hospitalized for COVID-19. DESIGN, SETTING, AND PARTICIPANTS In an ongoing, adaptive platform randomized clinical trial, 721 critically ill and 58 non–critically ill hospitalized adults were randomized to receive an RAS inhibitor or control between March 16, 2021, and February 25, 2022, at 69 sites in 7 countries (final follow-up on June 1, 2022). INTERVENTIONS Patients were randomized to receive open-label initiation of an ACE inhibitor (n = 257), ARB (n = 248), ARB in combination with DMX-200 (a chemokine receptor-2 inhibitor; n = 10), or no RAS inhibitor (control; n = 264) for up to 10 days. MAIN OUTCOMES AND MEASURES The primary outcome was organ support–free days, a composite of hospital survival and days alive without cardiovascular or respiratory organ support through 21 days. The primary analysis was a bayesian cumulative logistic model. Odds ratios (ORs) greater than 1 represent improved outcomes. RESULTS On February 25, 2022, enrollment was discontinued due to safety concerns. Among 679 critically ill patients with available primary outcome data, the median age was 56 years and 239 participants (35.2%) were women. Median (IQR) organ support–free days among critically ill patients was 10 (–1 to 16) in the ACE inhibitor group (n = 231), 8 (–1 to 17) in the ARB group (n = 217), and 12 (0 to 17) in the control group (n = 231) (median adjusted odds ratios of 0.77 [95% bayesian credible interval, 0.58-1.06] for improvement for ACE inhibitor and 0.76 [95% credible interval, 0.56-1.05] for ARB compared with control). The posterior probabilities that ACE inhibitors and ARBs worsened organ support–free days compared with control were 94.9% and 95.4%, respectively. Hospital survival occurred in 166 of 231 critically ill participants (71.9%) in the ACE inhibitor group, 152 of 217 (70.0%) in the ARB group, and 182 of 231 (78.8%) in the control group (posterior probabilities that ACE inhibitor and ARB worsened hospital survival compared with control were 95.3% and 98.1%, respectively). CONCLUSIONS AND RELEVANCE In this trial, among critically ill adults with COVID-19, initiation of an ACE inhibitor or ARB did not improve, and likely worsened, clinical outcomes. TRIAL REGISTRATION ClinicalTrials.gov Identifier: NCT0273570

Recombination in Organic Bulk Heterojunction Solar Cells: Small Dependence of Interfacial Charge Transfer Kinetics on Fullerene Affinity

We investigate the causes for obtaining higher open-circuit voltage in solar cells that use a fullerene with a smaller electron affinity. Using impedance spectroscopy technique, we show that the change of fullerene LUMO energy has very little influence on the kinetic rate of charge transfer across the interface. In terms of the Marcus theory, large reorganization energy values govern the recombination kinetic rate, which is only slightly dependent on the fullerene LUMO energy, and also depends weakly on the energy location of recombining carriers within the broad density of states. Since the recombination rate is very similar in the different devices, we conclude that the larger open-circuit voltage is due to the larger donor HOMO/acceptor LUMO offse

Current-voltage characteristics of bulk heterojunction organic solar cells: connection between light and dark curves

A connection is established between recombination and series resistances extracted from impedance spectroscopy and current-voltage curves of polythiophene:fullerene organic solar cells. Recombination is shown to depend exclusively on the (Fermi level) voltage, which allows construction of the current-voltage characteristics in any required conditions based on a restricted set of measurements. The analysis highlights carrier recombination current as the determining mechanism of organic solar cell performance

Recombination in Organic Bulk Heterojunction Solar Cells: Small Dependence of Interfacial Charge Transfer Kinetics on Fullerene Affinity

We investigate the causes for obtaining higher open-circuit voltage in solar cells that use a fullerene with a smaller electron affinity. Using impedance spectroscopy technique, we show that the change of fullerene LUMO energy has very little influence on the kinetic rate of charge transfer across the interface. In terms of the Marcus theory, large reorganization energy values govern the recombination kinetic rate, which is only slightly dependent on the fullerene LUMO energy, and also depends weakly on the energy location of recombining carriers within the broad density of states. Since the recombination rate is very similar in the different devices, we conclude that the larger open-circuit voltage is due to the larger donor HOMO/acceptor LUMO offset

Alginate/Polypyrrole Hydrogels as Potential Extraction Phase for Determination of Atrazine, Caffeine, and Progesterone in Aqueous Samples

Hydrogels are smart-swelling 3D structures capable of incorporating/expelling water while maintaining their structures. When combined with electroactive materials, such as conducting polymers, the resulting composite may present tunable properties. Herein, the preparation and characterization of alginate-polypyrrole composite hydrogels is described using chemical polymerization to form polypyrrole inside and around alginate beads, employing two simple protocols. These materials were qualitatively tested as extraction phases, using the solid-phase extraction technique, for the pre-concentration of contaminants of emerging concern (atrazine, caffeine, and progesterone). Compared to alginate alone, the composite materials showed a modified extraction capacity, especially for the extraction of progesterone. It was shown that the alginate matrix also contributes to the extraction, not only acting as a support but also as an active extraction media, evidencing a good combination of materials