Luminescence from solutions of small semiconductor clusters (‘quantum dots’) of different sizes. By simply changing the size of the dots, we can change the colour of light they absorb or give out – so we can match the dots to the part of the solar spectrum we want to collect. (credit: Nanoco Technologies Ltd).
Professor Wendy Flavell, from The University of Manchester’s Photon Science Institute, and her colleagues are working to create a solar-nano device using ‘quantum dots’ – tiny clusters of semiconducting material which absorb sunlight. The scientists are working to build a solar ‘nanocell’ that will use the Sun’s energy directly to make important fuels or chemicals needed by industry. At the heart of the nanocell are two types of light-absorber – small semiconductor clusters called ‘quantum dots’, containing only a few hundred atoms, and porphyrin molecules (like those involved in photosynthesis). They are creating catalytic devices which harvest light energy using quantum dots, or photovoltaic materials to drive the formation of synthetic fuels from water or carbon dioxide can be viewed as artificial photosynthesis.
Nanoco is the world’s leading developer and manufacturer of quantum dots. Nanoco Group PLC and its operating subsidiary Nanoco Technologies Ltd partner major R&D and blue-chip industrial organisations in the development of applications incorporating semiconductor nanoparticles, “quantum dots”. Quantum dots are tiny particles, or “nanoparticles”, of a semiconductor material, traditionally chalcogenides (selenides or sulfides) of metals like cadmium or zinc (CdSe or ZnS, for example), which range from 2 to 10 nanometers in diameter (about the width of 50 atoms). Nanoco Technologies is the only manufacturer currently able to supply production quantities of these nanoparticles which do not use a regulated heavy metal. We are the only manufacturer able to respond to orders for large quantities of bespoke quantum dots, and we are leading the way in customising the functionalisation of quantum dots enabling chemical linkage for biological and other specific uses.
Scientists can select which color of sunlight is absorbed just by changing the size of the quantum dots. Catalyst molecules are grafted onto the surfaces of the dots, and these do the chemistry. When sunlight is absorbed, carriers of electric current are created (just as in a solar panel), but here they provide the potential to do useful chemistry with the catalyst – for example turning water into hydrogen fuel. This could be a green way of making the fuel for hydrogen-powered cars – instead of making it from fossil fuel as we do right now.
Nanoco Technology products
Functionalised quantum dots
Nanoco Technologies can alter the surface chemistry of all the varieties of quantum dots currently in production.
* Replacing the HDA capping agent with a water soluble polymer functionalises our quantum dots for use with chemical and biological reagents
* Replacing the HDA capping agent with an acid equivalent (COOH) functionalises our quantum dots for bonding into a host of different polymers and biomolecules
* Replacing the HDA capping agent with an amine group equivalent (NH2) functionalises our quantum dots for bonding into a host of different polymers and biomolecules
Electroluminescent quantum dots
Organic light emitting diode (OLED) displays represent the next generation of display technology. They promise wider viewing angles, thinner, lighter displays as well as improved energy efficiency.
Nanoco Technologies are working with partners to develop the next generation in OLED technology. OLEDs are characterised by an emissive layer that consists of organic molecules. To improve these devices we use quantum dots as the emissive material. Quantum dots have the following attractive properties:
* High photoluminescence quantum yield (efficiency)
* Solution processability (less costly fabrication)
* High stability (improved device lifetimes)
* Narrow emission bands (improved colour saturation)
* Tuneable emission via size, i.e. one material for many colours (less costly fabrication)
* Capability to emit light from 100 percent of electrically excited photons (efficiency)
Importantly, only one material is needed to generate a full colour display and because of the narrow emission bands the display will have a wider colour gamut. Thus QD-OLED displays offer better colour saturation than current display technologies (LCD, plasma, OLED).
Cadmium-based quantum dots tuned to emit different colours in the visible spectrum with enhanced longevity and stability.
Cadmium-free quantum dots that show bright emission and can be tuned from ultraviolet, through the visible spectrum, into infrared.
Copper Indium Gallium Diselenide nanoparticles for use in next-generation thin film solar cells, which can be fabricated using conventional printing techniques.
Water-soluble quantum dots
Water-soluble functionalised quantum dots, either based on Cadmium or Cadmium-free, in a range of bright and distinct colours.
Quantum dot beads
Polymer beads combine quantum dots of any required emission wavelength in a polymer matrix; microscopic in size, beads are supplied as an easy-to-handle, free-flowing powder.
CdSe and CdS quantum dot cores
Cadmium Selenide and Cadmium Sulphide quantum dot cores tuned to emit different colors in the visible spectrum.