Organic solar cells (OSCs) can be unstable under ultraviolet (UV) irradiation. To address this issue and enhance the power conversion efficiency (PCE), an inorganic‐perovskite/organic four‐terminal ...tandem solar cell (TSC) based on a semitransparent inorganic CsPbBr3 perovskite solar cell (pero‐SC) as the top cell and an OSC as bottom cell is constructed. The high‐quality CsPbBr3 photoactive layer of the planar pero‐SC is prepared with a dual‐source vacuum coevaporation method, using stoichiometric precursors of CsBr and PbBr2 with a low evaporation rate. The resultant opaque planar pero‐SC exhibits an ultrahigh open‐circuit voltage of 1.44 V and the highest reported PCE of 7.78% for a CsPbBr3‐based planar pero‐SC. Importantly, the devices show no degradation after 120 h UV light illumination. The related semitransparent pero‐SC can almost completely filter UV light and well maintain photovoltaic performance; it additionally shows an extremely high average visible transmittance. When it is used to construct a TSC, the top pero‐SC acting as a UV filter can utilize UV light for photoelectric conversion, avoiding the instability problem of UV light on the bottom OSC that can meet the industrial standards of UV‐light stability for solar cells, and leading to the highest reported PCE of 14.03% for the inorganic‐perovskite/organic TSC.
A wide‐bandgap and low‐defect‐concentration CsPbBr3 film is fabricated using the vacuum‐evaporation method, and the related solar cell shows a high efficiency and robust photostability. When constructing inorganic‐perovskite/organic tandem solar cells, the top CsPbBr3‐based semitransparent perovskite solar cells can be used to filter ultraviolet (UV) light and overcome the UV‐light stability problem of the organic solar cells; they also show a record efficiency of 14.03%.
2D materials, represented by transition metal dichalcogenides (TMDs), have attracted tremendous research interests in photoelectronic and electronic devices. However, for their relatively small ...bandgap (<2 eV), the application of traditional TMDs into solar‐blind ultraviolet (UV) photodetection is restricted. Here, for the first time, NiPS3 nanosheets are grown via chemical vapor deposition method. The nanosheets thinning to 3.2 nm with the lateral size of dozens of micrometers are acquired. Based on the various nanosheets, a linearity is found between the Raman intensity of specific Ag modes and the thickness, providing a convenient method to determine their layer numbers. Furthermore, a UV photodetector is fabricated using few‐layered 2D NiPS3 nanosheets. It shows an ultrafast rise time shorter than 5 ms with an ultralow dark current less than 10 fA. Notably, this UV photodetector demonstrates a high detectivity of 1.22 × 1012 Jones, outperforming some traditional wide‐bandgap UV detectors. The wavelength‐dependent photoresponsivity measurement allows the direct observation of an admirable cut‐off wavelength at 360 nm, which indicates a superior spectral selectivity. The promising photodetector performance, accompanied with the controllable fabrication and transfer process of nanosheet, lays the foundation of applying 2D semiconductors for ultrafast UV light detection.
Herein, a high‐performance ultraviolet photodetector based on a few‐layered 2D NiPS3 nanosheet is demonstrated. NiPS3 nanosheets are first synthesized by the chemical vapor deposition method and the thickness‐dependent Raman spectra are systematically investigated. A two‐terminal device based on NiPS3 nanosheets exhibits significant spectral selectivity. A rise time shorter than 5 ms and a detectivity of 1.22 × 1012 Jones are realized.
AlGaN‐based deep ultraviolet light‐emitting diodes (DUV LEDs) are featured with small size, DC driving, no environmental contamination etc., and they are now emerging as the excellent solid‐state ...light source to replace the conventional mercury based light tubes. Nevertheless, the DUV LEDs are currently affected by the poor external quantum efficiency (EQE), which is caused by the low internal quantum efficiency (IQE) and the very unsatisfying light extraction efficiency (LEE). In this work, the authors disclose the underlying mechanism for the low EQE and summarize the technologies that have been adopted so far for enhancing the EQE.
This paper comprehensively reviews III–V nitride based deep ultraviolet light‐emitting diodes (DUV LEDs), which are suffering from the low external quantum efficiency (EQE). This article conducts an in‐depth investigation on the issues that DUV LEDs are encountering now. The strategies that are taken by the research community to improve the EQE are summarized and analyzed.
Ultraviolet radiation and visible light both have biologic effects on the skin. Visible light can induce erythema in light-skinned individuals and pigmentation in dark-skinned individuals. ...Broad-spectrum sunscreens protect against ultraviolet radiation but do not adequately protect against visible light. For a sunscreen to protect against visible light, it must be visible on the skin. Inorganic filters (also known as mineral filters), namely, zinc oxide and titanium dioxide, are used in the form of nanoparticles in sunscreens to minimize the chalky and white appearance on the skin; as such, they do not protect against visible light. Tinted sunscreens use different formulations and concentrations of iron oxides and pigmentary titanium dioxide to provide protection against visible light. Many shades of tinted sunscreens are available by combining different amounts of iron oxides and pigmentary titanium dioxide to cater to all skin phototypes. Therefore, tinted sunscreens are beneficial for patients with visible light–induced photodermatoses and those with hyperpigmentation disorders such as melasma and postinflammatory hyperpigmentation.
Planar vacuum‐fluorescent‐display devices emitting polarized UV‐C, blue, and green light are demonstrated using immiscible Al1−xInxN nanostructures grown in nonpolar m‐directions. Despite the ...presence of high concentration of nonradiative recombination centers, the Al1−xInxN nanostructures emit polarized light with the luminescence lifetimes of 22–32 ps at 300 K. This defect‐resistant radiative performance suggests supernormal localized characteristics of electron–hole pairs.
In this study, the performances and mechanisms of UV/ferrate(VI) oxidation were investigated comprehensively using 2,4-dichlorophenol (2,4-DCP) as a probe compound. UV/ferrate(VI) oxidation could ...efficiently degrade 2,4-DCP and its oxidation ability outperformed conventional UV-based advanced oxidation processes. Moreover, the degradation process of 2,4-DCP followed the pseudo-first order kinetics. In the absence of phosphate buffer, the rate constant of 2,4-DCP degradation increased from 9.4 × 10−3 to 2.4 × 10−2 min−1 when pH value was increased from 3.0 to 6.0. However, the degradation was significantly inhibited by phosphate buffer at an identical pH due to the complexation of phosphate with the ferrate(VI) decay products. HCO3− appreciably accelerated the degradation of 2,4-DCP, while Cl− showed a negligible effect on the degradation. For the first time, combining with the results of chemical probe method, competitive kinetic experiment, electron spin resonance spectra and radical quenching studies, superoxide radicals were demonstrated as the dominant reactive species responsible for the degradation. On the basis of the intermediates detected by LC-MS/MS analysis, a pathway for 2,4-DCP degradation was proposed. This study provides a novel approach for contaminant removal using UV/ferrate(VI) oxidation and sheds new insights into the oxidation mechanisms.
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•The oxidation ability of UV/ferrate(VI) was superior to most UV-based AOPs.•UV/ferrate(VI) could oxidize 2,4-dichlorophenol efficiently.•Phosphate-buffered system inhibited the efficiency of UV/ferrate(VI) oxidation.•Superoxide radicals were main reactive species contributing to the degradation.•The generation of superoxide radicals was notably enhanced under UV irradiation.
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•Reactivity of multi-layer graphene (MLG) exposed to water, extreme UV light and H2.•Oxidation monitored by in-situ infrared spectroscopy.•As grown MLG does not oxidize, MLG ...transferred onto aSi does show oxidation.•Differences in reactivity attributed to (trapped) water at the interface.
In this work we expose transferred multi-layer graphene (i.e. graphene separated from the substrate used for graphene growth and placed onto a carrier sample) to Extreme Ultraviolet light and water, in the presence of hydrogen. It is observed that graphene oxidizes by breaking down its aromatic structure into the enol form of 1,3-diketone. Furthermore, this oxidation is compared with studies on as-grown multi-layer graphene samples, which are shown to not oxidize. Our work shows that oxidation is most likely limited to a few layers of graphene at the interface between the graphene and the substrate onto which it is transferred. This is attributed to the presence of water, trapped during the transfer process, which is dissociated by secondary electrons from the substrate.
Ultraviolet light-emitting diodes (UV-LEDs) have started replacing UV lamps. The power per LED of high-power LED products has reached 12 W (14 A), which is 100 times the values observed ten years ...ago. In addition, the cost of these high-power LEDs has been decreasing. In this study, we attempt to understand the technologies and potential of UV-LEDs.
Vitamin D is an important regulator of calcium and phosphorus homeostasis in animals. It can be acquired from the diet or synthesised de novo when skin is exposed to UVb. Vitamin D deficiency can ...lead to a complex of diseases collectively called metabolic bone disease (MBD). Diurnal lizards without access to UVb are prone to develop vitamin D deficiency, even when dietary vitamin D3 is provided. A trial was conducted to determine whether juvenile nocturnal lizards require access to UVb to prevent vitamin D deficiency. All leopard geckos (Eublepharis macularius) were supplemented with dietary vitamin D3. One group was exposed to low level UVb radiation (33–51 μW/cm2) from hatching until 6 months of age and a second group remained unexposed. Animals were fed ad libitum and their growth and weight gain compared with non-exposed controls. At the end of the trial, blood samples were analysed for vitamin D3 metabolites. The concentration of the vitamin D3 metabolite, 25(OH)D3, was higher in UVb exposed animals (61 ± 20 vs. 38 ± 8 nmol/L), confirming cutaneous synthesis with UVb exposure. Growth and weight gain were similar in both groups, and this, together with the absence of clinical symptoms, suggests that dietary vitamin D3 alone can meet the vitamin D requirements for growth of this nocturnal gecko, during the first six months of life. It remains to be investigated whether the higher vitamin D metabolite levels holds other health benefits for this species, such as improved bone density or immune response.
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•The nocturnal leopard gecko synthesizes vitamin D3 when exposed to UVb.•Low UVb (UVI ≤ 1.6) for 2 h daily increases 25(OH)D3 levels by 50%.•Dietary vitamin D3 maintains normal growth and weight gain in juvenile leopard geckos.
Ultraviolet (UV) disinfection is an early discovered technology that is currently and widely used for water treatment and food hygiene treatment. A newly emerging technology of UV disinfection, that ...is, UV light-emitting diodes (UV-LEDs), has aroused considerable research attention. UV-LEDs feature numerous advantages compared with traditional UV mercury vapor lamps and are expected to replace traditional UV lamps. Researchers currently perform studies to obtain data and develop methods for UV-LED water treatment systems. This article analyzes the latest research status and discusses the types of inactivation factors, such as the wavelength selectivity of UV light source, control of UV dose, effect of inactivation rate constant (K) (cm2/mJ), working mode of water sample, external auxiliary system, and UV sensitivity of pathogenic bacteria in water. The wavelengths of approximately 260 and 280 nm normally feature strong inactivation characteristics. When compared with the approximately 260 nm wavelength chip, the around 280 nm wavelength chip proves to be a better choice as its higher wavelength light power can result in faster disinfection capacity of bacteria. UV dose can also be used as the reference value for disinfection of drinking water, whereas the inactivation rate constant (K) (cm2/mJ) varies with different microorganism internal structures. Changing the working mode or adding an auxiliary system can also enhance the inactivation effect in water treatment system settings. In addition, we can compare the inactivation capacities of several pathogens as follows: ΦX174 > Escherichia coli > T type bacteriophage >Bacillus subtilis > MS2 or Qβ > human adenovirus. The in-depth investigation and discussion of inactivation factors and the mechanism of action in UV-LEDs water treatment systems will establish a more efficient UV-LED disinfection method in the future, provide a guiding direction, and promote the standardization and normalization of pathogen inactivation mechanism in UV-LED water treatment systems.
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•The latest researches on ultraviolet light-emitting diodes (UV-LEDs) for water disinfection are reviewed.•The disinfection mechanism by UV-LEDs is discussed in detail.•The influence rule of UV-LED light source system parameters is illustrated.•The influence rule of UV-LED water treatment system settings is also presented.•Conclusions and future suggestions for UV-LEDs water disinfection are proposed.
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