8 research outputs found
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Advances in Solar-Driven Hygroscopic Water Harvesting.
Water scarcity is one of the greatest global challenges at this time. Significant efforts have been made to harvest water from the air, due to widely available water sources present in the atmosphere. Particularly, solar-driven hygroscopic water harvesting based on the adsorption-desorption process has gained tremendous attention because of the abundance of solar energy in combination with substantial improvements in conversion efficiency enabled by advanced sorbents, improved photothermal materials, interfacial heating system designs, and thermal management in recent years. Here, recent developments in atmospheric water harvesting are discussed, with a focus on solar-driven hygroscopic water harvesting. The diverse structural designs and engineering strategies that are being used to improve the rate of the water production, including the design principles for sorbents with high adsorption capacity, high-efficiency light-to-heat conversion, optimization of thermal management, vapor condensation, and water collection, are also explored. The current challenges and future research opportunities are also discussed, providing a roadmap for the future development of solar-driven hygroscopic water harvesting technology
Coexistence of negative photoconductivity and hysteresis in semiconducting graphene
Solution-processed graphene quantum dots (GQDs) possess a moderate bandgap, which make them a promising candidate for optoelectronics devices. However, negative photoconductivity (NPC) and hysteresis that happen in the photoelectric conversion process could be harmful to performance of the GQDs-based devices. So far, their origins and relations have remained elusive. Here, we investigate experimentally the origins of the NPC and hysteresis in GQDs. By comparing the hysteresis and photoconductance of GQDs under different relative humidity conditions, we are able to demonstrate that NPC and hysteresis coexist in GQDs and both are attributed to the carrier trapping effect of surface adsorbed moisture. We also demonstrate that GQDs could exhibit positive photoconductivity with three-order-of-magnitude reduction of hysteresis after a drying process and a subsequent encapsulation. Considering the pervasive moisture adsorption, our results may pave the way for a commercialization of semiconducting graphene-based and diverse solution-based optoelectronic devices
Photogenerated Carriers Transfer in Dye–Graphene–SnO<sub>2</sub> Composites for Highly Efficient Visible-Light Photocatalysis
The
visible-light-driven photocatalytic activities of graphene-semiconductor
catalysts have recently been demonstrated, however, the transfer pathway
of photogenerated carriers especially where the role of graphene still
remains controversial. Here we report graphene–SnO<sub>2</sub> aerosol nanocomposites that exhibit more superior dye adsorption
capacity and photocatalytic efficiency compared with pure SnO<sub>2</sub> quantum dots, P25 TiO<sub>2</sub>, and pure graphene aerosol
under the visible light. This study examines the origin of the visible-light-driven
photocatalysis, which for the first time links to the synergistic
effect of the cophotosensitization of the dye and graphene to SnO<sub>2</sub>. We hope this concept and corresponding mechanism of cophotosensitization
could provide an original understanding for the photocatalytic reaction
process at the level of carrier transfer pathway as well as a brand
new approach to design novel and versatile graphene-based composites
for solar energy conversion
Direct Conversion of Perovskite Thin Films into Nanowires with Kinetic Control for Flexible Optoelectronic Devices
With
significant progress in the past decade, semiconductor nanowires have
demonstrated unique features compared to their thin film counterparts,
such as enhanced light absorption, mechanical integrity and reduced
therma conductivity, etc. However, technologies of semiconductor thin
film still serve as foundations of several major industries, such
as electronics, displays, energy, etc. A direct path to convert thin
film to nanowires can build a bridge between these two and therefore
facilitate the large-scale applications of nanowires. Here, we demonstrate
that methylammonium lead iodide (CH<sub>3</sub>NH<sub>3</sub>PbI<sub>3</sub>) nanowires can be synthesized directly from perovskite film
by a scalable conversion process. In addition, with fine kinetic control,
morphologies, and diameters of these nanowires can be well-controlled.
Based on these perovskite nanowires with excellent optical trapping
and mechanical properties, flexible photodetectors with good sensitivity
are demonstrated