Semiconductor nanocrystals or also called quantum dots exhibit outstanding optical properties compared to organic dyes. Due to the quantum confinement their emission color can be continuously tuned from the ultraviolet to the near infrared range by changing the size and chemical composition.
They exhibit a broad absorption spectrum, a narrow emission band and large absorption cross sections. Their surface can be covered by a few monolayers of different semiconductor materials in such a way that we can either improve their luminescent properties and stability or avoid the fluorescence to obtain charge carriers. The latter effect opens tremendous alternatives in photovoltaics. Due to their optical properties, semiconductor nanoparticles are studied in different disciplines, from optics to biomedicine.
Thanks to a remarkable effort in the synthetic activities in the last 20 years, we can nowadays produce nanoparticles of different materials controlling their size, shape, and surface properties. Examples of nanoparticles produced by non hydrolytic colloidal synthetic methods are CdS, CdTe, InP, GaAs, PbS, or PbSe. However, the most studied system is CdSe, with tunable emission from blue to red. Due to the synthetic approach (hot injection method), the surface of these nanoparticles is capped with an organic shell that protects them and makes them stable in non-polar organic solvents. It is also possible to controllably replace the initial organic shell for water compatible ones. The organic shell plays a relevant role in the quantum efficiency of the nanoparticles and their stability in different media. However, this shell prevents high electrical conduction.
Carbon nanotubes are another example of nanomaterials with extraordinary electrical properties. They consist of one or several rolled up graphene layers. In the case of a single layer they are called single-wall and multi-wall when several layers are rolled-up. Hybrid materials composed of semiconductor nanoparticles and carbon nanotubes combine the high absorption properties of the former and the high electrical conductivity of the latter. One of the main drawbacks in the formation of such hybrid structures focuses on the type of interaction between them. Most of the existing procedures involve the growth of nanoparticles on previous defect sites provoked on the surface or edges of carbon nanotubes by aggressive chemical means. These aggressive treatments render an oxidized nanotube surface or even structural damage that deteriorates their outstanding electrical, mechanical, and optical properties significantly. Thus, supramolecular or electrostatic functionalisations are better approaches for photovoltaic applications.
Dr Beatriz H. Juárez, from IMDEA Nanoscience, works on the preparation of hybrid materials with high coverage without modifying the electrical properties of the tubes. Furthermore, the monodispersity of the nanoparticles with high crystallographic quality and a close contact between nanoparticles and nanotubes are also under investigation. The composites show photoelectrical response, injecting charge carriers in the nanotubes upon nanoparticle excitation. Although in an initial stage, the results obtained up to now points out the high potential of these composites to build up photovoltaic devices and solar cells.
B. H. Juárez, C. Klinke, A. Kornowski, H. Weller, Nano Letters, 2007, 7, 3564
IMDEA | alfa
Further reports about: > Cells > HYBRID > Hybrid Material > Nanoscience > Photovoltaics > SOLAR > Semiconductor > Semiconductor nanocrystals > carbon nanotubes > fluorescence > hydrolytic colloidal synthetic methods > light emitting diodes > luminescent properties > nanoparticles > photovoltaic devices > solar cells
Subnano lead particles show peculiar decay behavior
25.04.2018 | Ernst-Moritz-Arndt-Universität Greifswald
Getting electrons to move in a semiconductor
25.04.2018 | American Institute of Physics
At the Hannover Messe 2018, the Bundesanstalt für Materialforschung und-prüfung (BAM) will show how, in the future, astronauts could produce their own tools or spare parts in zero gravity using 3D printing. This will reduce, weight and transport costs for space missions. Visitors can experience the innovative additive manufacturing process live at the fair.
Powder-based additive manufacturing in zero gravity is the name of the project in which a component is produced by applying metallic powder layers and then...
Physicists at the Laboratory for Attosecond Physics, which is jointly run by Ludwig-Maximilians-Universität and the Max Planck Institute of Quantum Optics, have developed a high-power laser system that generates ultrashort pulses of light covering a large share of the mid-infrared spectrum. The researchers envisage a wide range of applications for the technology – in the early diagnosis of cancer, for instance.
Molecules are the building blocks of life. Like all other organisms, we are made of them. They control our biorhythm, and they can also reflect our state of...
University of Connecticut researchers have created a biodegradable composite made of silk fibers that can be used to repair broken load-bearing bones without the complications sometimes presented by other materials.
Repairing major load-bearing bones such as those in the leg can be a long and uncomfortable process.
Study published in the journal ACS Applied Materials & Interfaces is the outcome of an international effort that included teams from Dresden and Berlin in Germany, and the US.
Scientists at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) together with colleagues from the Helmholtz-Zentrum Berlin (HZB) and the University of Virginia...
Novel highly efficient and brilliant gamma-ray source: Based on model calculations, physicists of the Max PIanck Institute for Nuclear Physics in Heidelberg propose a novel method for an efficient high-brilliance gamma-ray source. A giant collimated gamma-ray pulse is generated from the interaction of a dense ultra-relativistic electron beam with a thin solid conductor. Energetic gamma-rays are copiously produced as the electron beam splits into filaments while propagating across the conductor. The resulting gamma-ray energy and flux enable novel experiments in nuclear and fundamental physics.
The typical wavelength of light interacting with an object of the microcosm scales with the size of this object. For atoms, this ranges from visible light to...
13.04.2018 | Event News
12.04.2018 | Event News
09.04.2018 | Event News
25.04.2018 | Physics and Astronomy
25.04.2018 | Physics and Astronomy
25.04.2018 | Information Technology