Colloidal cesium
lead iodide (CsPbI3) perovskite quantum
dots (QDs) are promising materials for solar cells because of their
suitable optical bandgap and the ease of solution-based processing
into large-area films. Herein, we report a synthetic strategy to build
up a colloidal CsPbI3/PbSe heterostructure, which not only
improves the absorption of sunlight but also passivates the surface
of perovskite QDs, which results in a lower trap density and prolonged
exciton lifetimes. Moreover, the presence of the PbSe component modifies
the electronic properties of the composite films, by changing the
CsPbI3 QD film from n-type to more ambipolar behavior,
thus helping to promote carrier separation and collection. These improvements
result in high-performance CsPbI3/PbSe QD solar cells with
a power conversion efficiency of 13.9% and improved storage stability
against moisture, benefiting from the hydrophobic protective coating
resulting from the presence of PbSe component.
SnS nanocrystals have been synthesized in a simple and facile way. Sn(6)O(4)(OH)(4) is introduced to synthesize tin sulfide, which is used as tin precursor. By changing the reaction conditions (reaction temperature and Sn/S molar ratio), SnS nanocrystals with different shape and size can be produced. SnS nanoparticles and nanoflowers with orthorhombic crystal structure have uniform size distribution. The SnS nanoflowers firstly transform to polycrystalline nanoflowers, and then become amorphous nanosheets. The drive force of amorphization reduces the high free-energy of nanocrystals. The layered crystal structure of SnS is the main reason for the shape evolution and amorphization processes. The optical properties of nanoparticles are investigated by optical absorption spectra. The optical direct band gap and optical indirect band gap in SnS nanoparticles are 3.6 eV and 1.6 eV, respectively. Compared to direct band gap (1.3 eV) and indirect band gap (1.09 eV) in bulk SnS, both direct transition and indirect transition in nanoparticles show an obvious quantum-size effect.
This paper develops a facile solution-based method to synthesize hollow Cu2-x Te nanocrystals (NCs) with tunable interior volume based on the Kirkendall effect. Transmission electron microscopy images and time-dependent absorption spectra reveal the temporal growth process from solid copper nanoparticles to hollow Cu2-x Te NCs. Furthermore, the as-prepared hollow Cu2-x Te NCs show enhanced sensitivity for the detection of carbon monoxide (CO), which is often referred to as the "silent killer". The response and recovery time of the as-prepared sensor for the detection of 100 ppm CO gas are estimated to be about 21 and 100 s, respectively, which are sufficient to render it a promising candidate for effective CO gas-sensing applications. Such enhanced performance is achieved owing to the small grain size and large specific area of the hollow nanostructures. Therefore, the obtained hollow NCs based on the Kirkendall effect may have the potential as new functional blocks for high-performance gas sensors.
Hierarchical SnO nanocrystals are synthesized by a reproducible and facile way via decomposition of an intermediate product tin oxide hydroxide, Sn6O4(OH)4. By changing the amount of injecting water, layer-plate-like, nest-like, stepwise-bipyramid-like, and defective stepwise-bipyramid-like hierarchical SnO nanocrystals could be obtained. All of these hierarchical SnO nanostructures are constructed by smaller nanosheets. The driving force of aggregation is reducing the surface energy of nanocrystals. Water played a key role in the control morphologies of hierarchical SnO nanostructures. The water control decomposition (WCD) mechanism was proposed to explain the effect of water on the morphologies. On the basis of reaction kinetics, the different superfluous injected water after reaction would restrain the decomposition of Sn6O4(OH)4 to SnO nanosheets; a different amount of superfluous injected water would induce a different reaction rate. At different reaction rates, SnO nanosheets would have different sizes and different approaches to aggregation, and different hierarchical SnO nanocrystals appeared by injecting different amounts of water into the reaction. Typically, hierarchical SnO nanocrystals as an anode material for lithium ion batteries are studied. These SnO nanocrystals show good potential for lithium battery materials. Among these SnO nanostructures, the stepwise-bipyramid-like nanostructure shows the best properties.
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