Solar cells based on polycrystalline Cu(In,Ga)Se(2) absorber layers have yielded the highest conversion efficiency among all thin-film technologies, and the use of flexible polymer films as ...substrates offers several advantages in lowering manufacturing costs. However, given that conversion efficiency is crucial for cost-competitiveness, it is necessary to develop devices on flexible substrates that perform as well as those obtained on rigid substrates. Such comparable performance has not previously been achieved, primarily because polymer films require much lower substrate temperatures during absorber deposition, generally resulting in much lower efficiencies. Here we identify a strong composition gradient in the absorber layer as the main reason for inferior performance and show that, by adjusting it appropriately, very high efficiencies can be obtained. This implies that future manufacturing of highly efficient flexible solar cells could lower the cost of solar electricity and thus become a significant branch of the photovoltaic industry.
Organic-inorganic hybrid solar cells that combine a mesoporous scaffold, a perovskite light absorber and an organic hole transporter have emerged at the forefront of solution-processable photovoltaic ...devices; however, they require processing temperatures of up to 500 °C to sinter the mesoporous metal-oxide support. Here, we report the use of a thin film of ZnO nanoparticles as an electron-transport layer in CH3 NH3 PbI3 -based solar cells; in contrast to mesoporous TiO2 , the ZnO layer is both substantially thinner and requires no sintering. We took advantage of these facts to prepare flexible solar cells with power-conversion efficiencies in excess of 10%. The use of ZnO also results in improvements to device performance for cells prepared on rigid substrates. Solar cells based on this design exhibit power-conversion efficiencies as high as 15.7% when measured under AM1.5G illumination, which makes them some of the highest-performing perovskite solar cells reported to date.
Thin-film photovoltaics play an important role in the quest for clean renewable energy. Recently, methylammonium lead halide perovskites were identified as promising absorbers for solar cells. In the ...three years since, the performance of perovskite-based solar cells has improved rapidly to reach efficiencies as high as 15%. To date, all high-efficiency perovskite solar cells reported make use of a (mesoscopic) metal oxide, such as Al2 O3 , TiO2 or ZrO2 , which requires a high-temperature sintering process. Here, we show that methylammonium lead iodide perovskite layers, when sandwiched between two thin organic charge-transporting layers, also lead to solar cells with high power-conversion efficiencies (12%). To ensure a high purity, the perovskite layers were prepared by sublimation in a high-vacuum chamber. This simple planar device structure and the room-temperature deposition processes are suitable for many conducting substrates, including plastic and textiles.
A method of fabricating ultrathin (≈22–53 nm thick) graphene nanofiltration membranes (uGNMs) on microporous substrates is presented for efficient water purification using chemically converted ...graphene (CCG). The prepared uGNMs show well packed layer structure formed by CCG sheets, as characterized by scanning electron microscopy, atomic force microscopy, and transmission electron microscopy. The performance of the uGNMs for water treatment was evaluated on a dead end filtration device and the pure water flux of uGNMs was high (21.8 L m−2 h−1 bar−1). The uGNMs show high retention (>99%) for organic dyes and moderate retention (≈20–60%) for ion salts. The rejection mechanism of this kind of negatively charged membranes is intensively studied, and the results reveal that physical sieving and electrostatic interaction dominate the rejection process. Because of the ultrathin nature of uGNMs, 34 mg of CCG is sufficient for making a square meter of nanofiltration membrane, indicating that this new generation graphene‐based nanofiltration technology would be resource saving and cost‐effective. The integration of high performance, low cost, and simple solution‐based fabrication process promises uGNMs great potential application in practical water purification.
Ultrathin graphene nanofiltration membranes (uGNMs) are fabricated on microporous substrates. These graphene membranes (no more than 53‐nm thick) are thin enough to have excellent flexibility and can be bent without any breakage. The uGNMs show high pure water flux and high retention for organic dyes. The dark red Direct Red 81 solution turns into colorless after filtration.
Under illumination, metal nanoparticles can turn into ideal nanosources of heat due to enhanced light absorption at the plasmonic resonance wavelength. In this article, we aim at providing a ...comprehensive description of the generation of microbubbles in a liquid occurring around plasmonic nanoparticles under continuous illumination. We focus on a common situation where the nanoparticles are located on a solid substrate and immersed in water. Experimentally, we evidenced a series of singular phenomena: (i) the bubble lifetime after heating can reach several minutes, (ii) the bubbles are not made of water steam but of air, and (iii) the local temperature required to trigger bubble generation is much larger than 100 °C: This last observation evidences that superheated liquid water, up to 220 °C, is easy to achieve in plasmonics, under ambient pressure conditions and even over arbitrary large areas. This could lead to new chemical synthesis approaches in solvothermal chemistry.
Membrane distillation (MD) is a promising process for the treatment of highly saline wastewaters. The central component of MD is a stable porous hydrophobic membrane with a large liquid–vapor ...interface for efficient water vapor transport. A key challenge for current polymeric or hydrophobically modified inorganic membranes is insufficient operating stability, resulting in some issues such as wetting, fouling, flux, and rejection decline. This study presents an overall conceptual design and application strategy for a superhydrophobic ceramic–based carbon nanotube (CNT) desalination membrane having specially designed membrane structures with unprecedented operating stability and MD performance. Superporous and superhydrophobic surface structures with CNT networks are created after quantitative regulation of in situ grown CNT. The fully covered CNT layers (FC–CNT) exhibit significantly improved thermally and superhydrophobically stable properties under an accelerated stability test. Due to the distinctive structure of the superporous surface network, providing a large liquid–vapor superhydrophobic interface and interior finger-like macrovoids, the FC–CNT membrane exhibits a stable high flux with a 99.9% rejection of Na+, outperforming existing inorganic membranes. Under simple and nondestructive electrochemically assisted direct contact MD (e-DCMD), enhanced antifouling performance is observed. The design strategy is broadly applicable to be extended toward fabrication of high performance membranes derived from other ceramic or inorganic substrates and additional applications in wastewater and gas treatment.
Sustainable hydrogen production through photoelectrochemical water splitting using hematite (α-Fe2O3) is a promising approach for the chemical storage of solar energy, but is complicated by the ...material’s nonoptimal optoelectronic properties. Nanostructuring approaches have been shown to increase the performance of hematite, but the ideal nanostructure giving high efficiencies for all absorbed light wavelengths remains elusive. Here, we report for the first time mesoporous hematite photoelectodes prepared by a solution-based colloidal method which yield water-splitting photocurrents of 0.56 mA cm−2 under standard conditions (AM 1.5G 100 mW cm−2, 1.23 V vs reversible hydrogen electrode, RHE) and over 1.0 mA cm−2 before the dark current onset (1.55 V vs RHE). The sintering temperature is found to increase the average particle size, and have a drastic effect on the photoactivity. X-ray photoelectron spectroscopy and magnetic measurements using a SQUID magnetometer link this effect to the diffusion and incorporation of dopant atoms from the transparent conducting substrate. In addition, examining the optical properties of the films reveals a considerable change in the absorption coefficient and onset properties, critical aspects for hematite as a solar energy converter, as a function of the sintering temperature. A detailed investigation into hematite’s crystal structure using powder X-ray diffraction with Rietveld refinement to account for these effects correlates an increase in a C 3v -type crystal lattice distortion to the improved optical properties.
Zusammenfassung
Organofunktionelle Silanhaftvermittler sind hybride, multi‐funktionelle Verbindungen, welche in einer Vielzahl von Anwendungen zur Verbesserung der Adhäsion eingesetzt werden können. ...Aufgabe der Silanhaftvermittler ist es, eine möglichst gute Verträglichkeit und effektive Anbindung der beiden Partner in der Grenzflächenschicht zu schaffen. Silanhaftvermittler finden Anwendung bei der Oberflächenfunktionalisierung von Füllstoffen, Fasern oder Substraten; der reaktiven Compoundierung von mit Fasern oder Füllstoffen verstärkten Kunststoffen oder Gummi sowie als adhäsionsverstärkendes Additiv in flüssigen oder pastösen Produktformulierungen. In diesem zweiten Teil der Artikelserie werden Anwendungen aus den genannten Bereichen beispielhaft vorgestellt. Die aufgeführten Beispiele zeigen, dass die Auswahl eines geeigneten Silanhaftvermittlers recht komplex sein kann, insbesondere wenn dieser als adhäsionsverstärkendes Additiv in flüssigen oder pastösen Produktformulierungen eingesetzt werden soll.
Summary
Organofunctional silane coupling agents are hybrid, multi‐functional compounds that can be used in a multitude of applications to improve adhesion. The function of silane coupling agents is to create the best possible compatibility and effective binding of the two partners within the interfacial layer. Silane coupling agents are applied in the surface functionalization of fillers, fibers or substrates; the reactive compounding of plastics or rubber reinforced with fibers or fillers; and as adhesion‐enhancing additives in liquid or paste‐like product formulations. In this second part of the article series, various examples of applications in the above‐mentioned areas are presented. The examples presented show that the selection of a suitable silane coupling agent can be quite complex, especially if it is to be used as an adhesion‐enhancing additive in liquid or paste‐like product formulations.
Haftvermittler verbessern die Adhäsion von flüssig applizierten, polymeren Werkstoffen zu Füllstoffen und Untergründen, indem sie die Grenzfläche durch eine graduelle Übergangsphase ersetzen. Eine technisch besonders wichtige Klasse von Haftvermittlern sind organisch funktionalisierte Silane und niedermolekulare, oligomere Siloxane. Der erste Teil dieser zweiteiligen Artikelserie befasste sich mit der Funktion und dem Chemismus der organisch funktionalisierten Silanhaftvermittler. In diesem zweiten Teil werden verschiedene Anwendungen aus den Bereichen Oberflächenfunktionalisierung von Füllstoffen, Fasern oder Substraten; reaktive Compoundierung sowie adhäsionsverstärkende Additivierung für flüssige oder pastöse Produktformulierungen (Abbildung 1) beispielhaft vorgestellt. Zur Erläuterung der Fachbegriffe ist Online ein Glossar verfügbar.
Within urban agriculture (UA), integrated rooftop greenhouses (i-RTG) have great growth potential as they offer multiple benefits. Currently it is intended to improve environmental benefits by taking ...advantage of the water, nutrients and gases flows. On the other hand, solid waste (SW) generated by the UA is a new type of waste within cities that has not well been classified or quantified for its use. This could become a new problem for the waste management system within cities in the future, mainly the organic fraction.
The objective of this research is to identify what type of i-RTG SW has the potential to be used from a circular economy (CE) perspective and propose a type of management for its material valorization.
The results of the case study show that, of the SW generated in i-RTG, the biomass has the greatest potential to be used locally as an eco-material, particularly the tomato stems. Its use is proposed as a substrate for two experimental lettuce crops in i-RTG. The results show that tomato stems have a better yield as a substrate after a prewash treatment, since at first the values of electrical conductivity (EC) are very high with respect to the control substrate, which is expanded perlite.
In conclusion, we can say that it is possible to increase the environmental benefits of i-RTG by taking advantage of its biomass locally, helping to foresee a possible future problem regarding the management of the residual biomass of i-RTG within cities. In this way, the paradigm about the perception of the SW of the UA could be changed to give them a by-product treatment from the beginning.
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•Solid waste (SW) from urban agriculture (UA): a new typology of waste within cities•Use of UA SW from a circular economy (CE) perspective•Biomass as a by-product of integrated rooftop greenhouse (i-RTG)•Use of tomato stems from i-RTG as a substrate for lettuce crops•Reduction of the UA SW within the cities and closure of the UA life cycle
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