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Polaron-induced exciton quenching in thermally activated delayed fluorescence (TADF)-based organic light-emitting diodes (OLEDs) can lead to external quantum efficiency (EQE) roll-off and device degradation. In this study, singlet-polaron annihilation (SPA) and triplet-polaron annihilation (TPA) were investigated under steady-state conditions and their relative contributions to EQE roll-off were quantified, using experimentally obtained parameters. It is observed that both TPA and SPA can lead to efficiency roll-off in 2,4,5,6-tetra(9 H -carbazol-9-yl)isophthalonitrile (4CzIPN) doped OLEDs. Charge imbalance and singlet-triplet annihilation (STA) were found to be the main contributing factors, whereas the device degradation process is mainly dominated by TPA. It is also shown that the impact of electric field-induced exciton dissociation is negligible under the DC operation regime (electric field < 0.5 MV cm −1 ). Through theoretical simulation, it is demonstrated that improvement to the charge recombination rate may reduce the effect of polaron-induced quenching, and thus significantly decrease the EQE roll-off. Efficiency roll-off in organic light-emitting diodes under elevated current densities not only results in high power consumption but also device degradation. Here, the impact of polaroninduced quenching in efficiency roll-off was investigated and strategies to reduce efficiency roll-off were proposed.

Perovskite light-emitting diodes are promising for next-generation lighting and displays because of their high colour purity and performance1. Although the management of singlet and triplet excitons is fundamental to the design of efficient organic light-emitting diodes, the nature of how excitons affect performance is still not clear in perovskite2–4 and quasi-two-dimensional (2D) perovskite-based devices5–9. Here, we show that triplet excitons are key to efficient emission in green quasi-2D perovskite devices and that quenching of triplets by the organic cation is a major loss path. Employing an organic cation with a high triplet energy level (phenylethylammonium) in a quasi-2D perovskite based on formamidinium lead bromide yields efficient harvesting of triplets. Furthermore, we show that upconversion of triplets to singlets can occur, making 100% harvesting of electrically generated excitons potentially possible. The external quantum and current efficiencies of our green (527 nm) devices reached 12.4% and 52.1 cd A−1, respectively.Careful harvesting of triplet excitons allows the realization of efficient green-emitting quasi-2D perovskite LEDs.

Organic light-emitting diode (OLED) technology is promising for applications in next-generation displays and lighting. However, it is difficult—especially in large-area mass production—to cover a large substrate uniformly with organic layers, and variations in thickness cause the formation of shunting paths between electrodes 1 , 2 , thereby lowering device production yield. To overcome this issue, thicker organic transport layers are desirable because they can cover particles and residue on substrates, but increasing their thickness increases the driving voltage because of the intrinsically low charge-carrier mobilities of organics. Chemical doping of organic layers increases their electrical conductivity and enables fabrication of thicker OLEDs 3 , 4 , but additional absorption bands originating from charge transfer appear 5 , reducing electroluminescence efficiency because of light absorption. Thick OLEDs made with organic single crystals have been demonstrated 6 , but are not practical for mass production. Therefore, an alternative method of fabricating thicker OLEDs is needed. Here we show that extraordinarily thick OLEDs can be fabricated by using the organic–inorganic perovskite methylammonium lead chloride, CH 3 NH 3 PbCl 3 (MAPbCl 3 ), instead of organics as the transport layers. Because MAPbCl 3 films have high carrier mobilities and are transparent to visible light, we were able to increase the total thickness of MAPbCl 3 transport layers to 2,000 nanometres—more than ten times the thickness of standard OLEDs—without requiring high voltage or reducing either internal electroluminescence quantum efficiency or operational durability. These findings will contribute towards a higher production yield of high-quality OLEDs, which may be used for other organic devices, such as lasers, solar cells, memory devices and sensors. Extraordinarily thick organic light-emitting diodes can be fabricated using hybrid organic–inorganic perovskites as the transport layers, thus relaxing fabrication constraints without affecting their efficiency, voltage requirement or durability.

Organic light-emitting diodes have become a mainstream display technology because of their desirable features. Third-generation electroluminescent devices that emit light through a mechanism called thermally activated delayed fluorescence are currently garnering much attention. However, unsatisfactory device stability is still an unresolved issue in this field. Here we demonstrate that electron-transporting n-type hosts, which typically include an acceptor moiety in their chemical structure, have the intrinsic ability to balance the charge fluxes and broaden the recombination zone in delayed fluorescence organic electroluminescent devices, while at the same time preventing the formation of high-energy excitons. The n-type hosts lengthen the lifetimes of green and blue delayed fluorescence devices by > 30 and 1000 times, respectively. Our results indicate that n-type hosts are suitable to realize stable delayed fluorescence organic electroluminescent devices. OLEDs based on thermally activated delayed fluorescence have shown high fluorescence efficiency but poor lifetime. Herein, Cui et al. demonstrate that the use of n-type host molecules can increase the device lifetime by 30 times and 1000 times for green and blue OLEDs, respectively.

The present study investigated the antioxidant activity, metal chelating ability and genoprotective effect of the hydroethanolic extracts of Crocus sativus stigmas (STG), tepals (TPL) and leaves (LV). We evaluated the antioxidant and metal (Fe2+ and Cu2+) chelating activities of the stigmas, tepals and leaves of C. sativus. Similarly, we examined the genotoxic and DNA protective effect of these parts on rat leukocytes by comet assay. The results showed that TPL contains the best polyphenol content (64.66 µg GA eq/mg extract). The highest radical scavenging activity is shown by the TPL (DPPH radical scavenging activity: IC50 = 80.73 µg/mL). The same extracts gave a better ferric reducing power at a dose of 50 µg/mL, and better protective activity against β-carotene degradation (39.31% of oxidized β-carotene at a 100 µg/mL dose). In addition, they showed a good chelating ability of Fe2+ (48.7% at a 500 µg/mL dose) and Cu2+ (85.02% at a dose of 500 µg/mL). Thus, the antioxidant activity and metal chelating ability in the C. sativus plant is important, and it varies according to the part and dose used. In addition, pretreatment with STG, TPL and LV significantly (p < 0.001) protected rat leukocytes against the elevation of percent DNA in the tail, tail length and tail moment in streptozotocin- and alloxan-induced DNA damage. These results suggest that C. sativus by-products contain natural antioxidant, metal chelating and DNA protective compounds, which are capable of reducing the risk of cancer and other diseases associated with daily exposure to genotoxic xenobiotics.

Ziziphus lotus (L.) Lam. (Rhamnaceae) is a plant species found across the Mediterranean area. This comprehensive overview aims to summarize the botanical description and ethnobotanical uses of Z. lotus and its phytochemical compounds derived with recent updates on its pharmacological and toxicological properties. The data were collected from electronic databases including the Web of Science, PubMed, ScienceDirect, Scopus, SpringerLink, and Google Scholars. It can be seen from the literature that Z. lotus is traditionally used to treat and prevent several diseases including diabetes, digestive problems, urinary tract problems, infectious diseases, cardiovascular disorders, neurological diseases, and dermal problems. The extracts of Z. lotus demonstrated several pharmacological properties in vitro and in vivo such as antidiabetic, anticancer, anti-oxidant, antimicrobials, anti-inflammatory, immunomodulatory, analgesic, anti-proliferative, anti-spasmodic, hepatoprotective, and nephroprotective effects. The phytochemical characterization of Z. lotus extracts revealed the presence of over 181 bioactive compounds including terpenoids, polyphenols, flavonoids, alkaloids, and fatty acids. Toxicity studies on Z. lotus showed that extracts from this plant are safe and free from toxicity. Thus, further research is needed to establish a possible relationship between traditional uses, plant chemistry, and pharmacological properties. Furthermore, Z. lotus is quite promising as a medicinal agent, so further clinical trials should be conducted to prove its efficacy.

Flaxseed is an oilseed (45–50% oil on a dry-weight basis) crop. Its oil has demonstrated multiple health benefits and industrial applications. The goal of this research was to evaluate the antidiabetic and anti-inflammatory potential of the free polyphenol fraction of flax (Linum usitatissimum L.) seeds (PLU), based on their use in traditional medicine. Mice with alloxan-induced diabetes were used to study the antidiabetic activity of PLU in vivo, with an oral administration of 25 and 50 mg/kg over 28 days. Measurements of body weight and fasting blood glucose (FBG) were carried out weekly, and biochemical parameters were evaluated. An oral glucose tolerance test was also performed. Inhibitory activities of PLU on α-amylase and α-glucosidase activities were evaluated in vitro. The anti-inflammatory was evaluated in vivo in Wistar rats using the paw edema induction Test by carrageenan, and in vitro using the hemolysis ratio test. PLU administration to diabetic mice during the study period improved their body weight and FBG levels remarkably. In vitro inhibitory activity of digestive enzymes indicated that they may be involved in the proposed mode of action of PLU extract. Qualitative results of PLU revealed the presence of 18 polyphenols. These findings support daily consumption of flaxseed for people with diabetes, and suggest that polyphenols in flaxseed may serve as dietary supplements or novel phytomedicines to treat diabetes and its complications.

The presence of pharmaceuticals in the environment has increased. These pollutants are toxic and non-biodegradable. Piroxicam (PRX) is a non-steroidal anti-inflammatory drug that ends up in wastewater via pharmaceutical industry activities and human being consumption. This work aimed to study the pharmaceutical pollutant removal from wastewater using agricultural by-products as low-cost adsorbent material. Different parameters were studied, such as time, initial adsorbate concentrations, and temperature. The study of the initial concentration-effect shows that the greatest amount of adsorbed is observed in low concentrations. The temperature has shown a negative effect in this study. The kinetics show that after 45min, the equilibrium is obtained; that means the exhaustion of all active sites. The representative model of this adsorption is the Langmuir isotherm according to the regression coefficient, which is equal to 0.99. The natural abundance of this material and the low cost of investment could offer a good alternative to other more expensive adsorbents such as activated carbon.

In Morocco, chloroquine/hydroxychloroquine + azithromycin have been used off-label for COVID-19 treatment. This study aimed to describe the distribution, nature and seriousness of the adverse drug reactions (ADRs) associated with the two drug combinations in COVID-19 in-patients. We conducted a prospective observational study based on intensive pharmacovigilance in national COVID-19 patients’ management facilities from April 1 to June 12, 2020. Hospitalized patients treated with chloroquine/hydroxychloroquine + azithromycin and who experienced ADRs during their hospital stay were included in the study. The causality and seriousness of the ADRs were assessed using the World Health Organization-Uppsala Monitoring Centre method and the agreed criteria in the ICH guideline (E2A) respectively. A total of 237 (51.7%) and 221 (48.3%) COVID-19 in-patients treated respectively with chloroquine + azithromycin and hydroxychloroquine + azithromycin experienced 946 ADRs. Serious ADRs occurred in 54 patients (11.8%). Gastrointestinal system was most affected both in patients taking chloroquine + azithromycin (49.8%) or hydroxychloroquine + azithromycin (54.2%), followed by nervous system and psychiatric. Eye disorders were more frequent in patients receiving chloroquine + azithromycin (10.3%) than those receiving hydroxychloroquine + azithromycin (1.2%). Cardiac ADRs accounted for 6.4% and 5.1% respectively. Chloroquine + azithromycin caused more ADRs by patients than hydroxychloroquine + azithromycin (2.6 versus 1.5 ADRs/patient). Causality assessment was possible for 75.7% of the ADRs. Diabetes was identified as a risk factor for serious ADRs (ORa 3.56; IC: 95% 1.5–8.6). The off-label use of the two drug combinations in COVID-19 in-patients according to the national therapeutic protocol seems to be safe and tolerable. ADRs were mainly expected. However, precaution should be taken in using the drugs in diabetic patients to prevent the risk of serious ADRs.

In the geotechnical engineering field, shallow foundations are frequently needed to ensure good fieldwork stability. They are also intended to permanently and uniformly transmit all load pressure on the seating floor. However, numerous mechanical constraints, such as bearing capacity of foundations, durability, stability, design of shallow foundations, lead, unfortunately, to a serious realization challenge. Finding an adequate solution presents the main goal and effort of both scholars and professionals. Indeed, the corresponding drawback is observed through the high number of reported damages that occurred in the structure of foundations and the punching failure.The failure mechanisms of shallow foundations, verified in full size or on scale models, show “sliding surfaces” and rigid (solid) blocks, which can be described with the kinematic method of rigid solids.The main objective of this study is the application of the kinematic method of rigid solids in the study of the stability of shallow foundations with respect to punching, the purpose of which is to determine the bearing capacity factors Nc, Nγ, and the passive earth pressure coefficient Kp of foundations. In this context, two mechanical models have been proposed with 5 and 7 rigid solids, and a program developed via the MathCAD environment is applied to check the validity of the two previous models. The kinematic method of rigid solids gives results very close and comparable with that of Caquot/Kerisel for the factors of the bearing capacity and passive earth pressure coefficient - the ratio Kp - according to the five- and seven-solid model.