Solar power is one of the most promising alternatives to using oil, gas and coal to generate the energy we need. The sunlight that reaches the earth from the Sun is enough to supply all our energy needs 10,000 times over. However, today's solar cells are not yet economic; it is still cheaper to produce power by burning fossil fuels and this is preventing their widespread use. How can we make solar cells economically competitive with fossil fuels? There are two ways: make them more cheaply or make them more efficient (or preferably both!) Most of the solar cells we use today are made from silicon and are up to around 20% efficient but expensive to make. Some newer, different types of cell are beginning to become available which are cheaper to make but are only 10% efficient at most. We need to develop solar cells that are both cheap and efficient enough to compete with fossil fuels. One of the most promising ways to do this is by using 'quantum dots' (QDs) - tiny clusters of a few hundred semiconductor atoms that absorb the sunlight and turn it into electricity. They are cheap and easy to make. We can change the colour of sunlight that is absorbed simply by changing the size of the QD. This means we can easily make a higher-efficiency 'multijunction' cell that absorbs more of the sunlight by using dots of several different sizes. This is not the only way in which QDs can lead to higher efficiency. In today's solar cells, about half of the energy from the Sun is wasted as heat when the sunlight is absorbed by the cell. In QDs, however, something else can happen - the energy that would become waste heat in a normal cell can be used instead to produce extra electricity. This is known as 'multiple exciton generation' or 'MEG'. Solar cells based on MEG in QDs could be up to 50% more efficient than today's technology. This is an exciting prospect but we still need to understand this process better. We need to find out what happens in the QD straight after sunlight is absorbed. MEG occurs extremely fast, and is hard to study, so it is difficult to prove whether MEG is happening in a QD or not. To tackle this, we have developed ultrafast laser experiments that give us a snapshot of the current as it is created. We use a very short laser pulse to replicate the sunlight, creating the current. Then we measure what has happened in the sample using a pulse of terahertz radiation (very low energy infrared). This is absorbed very strongly by the current carriers. If we vary the time between the 'pump' pulse and the 'probe' pulse, we can measure what happens to the current very quickly (in around 1/10,000,000,000th of a second). This gives us a measure of the extra electricity created by MEG. We can do this with semiconductor samples with a very large number of atoms, but the conventional terahertz radiation source we use is not powerful enough to study QD samples, which are very dilute. Much higher power compact terahertz sources are being developed in ASTeC at STFC Daresbury Laboratory. The purpose of this application is to use this STFC technology in our measurements to allow us to measure the current created by sunlight in QDs (and MEG), on very fast timescales. We will install and test a number of STFC terahertz sources in our experiments. Measurements like this are very important to the manufacturers of QDs. At the University of Manchester, we have been collaborating for some years with Nanoco Technologies Ltd, the UK's leading manufacturer of QDs. They are interested in the ways in which their dots might be used in future solar cells. In their in-house research they are developing solar cell prototypes that use QDs. In this project we will demonstrate the value of STFC-developed portable high power terahertz sources for QD measurements to Nanoco and the solar industry. At the end of this feasibility study, we hope to develop the technology in partnership with Nanoco and STFC.

Solar power is one of the most promising alternatives to using oil, gas and coal to generate the energy we need. Sunlight is freely available, safe and enough of it reaches the earth from the sun to supply all our energy needs 10,000 times over. It is also clean, releasing none of the carbon dioxide in to the atmosphere that fossil fuels do and which threatens to cause damaging climate change. However, today's solar cells are not yet economic; it is still cheaper to produce power by burning fossil fuels and this is preventing their wide-spread use. How can we make solar cells economically competitive with fossil fuels? There are two ways: make them more cheaply or make them more efficient, or preferably both! Most of the solar cells you see around today are made from silicon and are up to 20% efficient but are expensive to make. Some newer, different types of cell are beginnning to become available which are a lot cheaper to make but are only 10% efficient at most. The aim of this project is to have the best of both worlds - solar cells that are both cheap and efficient enough to compete with fossil fuels. The key part of these new cells will be 'quantum dots' - these are tiny crystals of semiconductor that will absorb the sunlight and turn it into electricity. In today's solar cells, about half of the energy from the sun is wasted as heat as soon as the sunlight is absorbed by the cell. In quantum dots, however, something else can happen - the energy that would become waste heat in a normal cell can be used instead to produce extra electricity. This means that solar cells based on quantum dots could be up to 50% more efficient than today's technology. This is an exciting prospect and could be important but we still need to understand this process better. In this project, we will produce new types of quantum dots which are designed to maximise the effciency with which sunlight is turned into electricity. These dots must also be made from materials which are cheap, abundant and safe. We will use X-rays to study their structure carefully and lasers to study what happens to the light as it is absorbed. Complex computer models will be used to help us better understand what is happening and make the conversion of sunlight to electricity as efficient as it can be. Finally, we will build a prototype solar cell using these new quantum dots which will demonstrate how they can be used to generate electricity safely, cleanly and cheaply.

The purpose of this project is to develop a novel photochemical atomic layer deposition (ALD) manufacturing technology to coat three - dimensional components and feedstock powders with ultrathin functional coatings. Conventional atomic layer deposition is already widely used in the displays and microelectronics industries. It is a thermo-chemical process where two precursor reagents are pulsed in cycles onto a heated work piece. The combination of the substrate temperature and the chemical reaction energy drive the process forward to deposit the thin film layer by layer. Because the process occurs on the surface, highly uniform and conformal layers can be deposited onto high-aspect ratio or porous materials with ultraprecise thickness control. The hypothesis for the proposed research is to use a photo-excitation process to activate one or both of the ALD chemical reagents so that they can react to deposit the thin film with a lower thermal input from a substrate heater. We will adapt the existing Round 1 ALD reactor at Liverpool to incorporate a larger scale chamber capable of containing: (1) an array of 3D components; and (2) reactor furniture for a fluidised bed powder treatment system. The modified system will be built to accommodate ultraviolet sources for the processing of 3D components or the treatment of powder beds. We also propose to use new UV source lamps to target the wavelength of the output from a range of commercially available UV lamp modules to photo-chemically decompose the precursors to form the film. The replacement chamber will also be manufactured to enable access for in-situ monitoring of the deposition process using an existing fibre-optic cable based Raman probe and a quartz crystal microbalance. These will provide feedback on the start of deposition as a function of illumination, substrate temperature, flow rates etc. If achieved, these objectives represent a significant advancement of existing ALD technology and would open up new applications where ultrathin functional materials can be exploited, such as display electronics, biomedical devices and photovoltaics amongst others.

Augmented reality (AR) has the power to seamlessly integrate the digital world with physical reality. It could provide surgeons with vital medical data as they operate, allow athletes to access training information seamlessly whilst playing sports and offers countless other opportunities in business, leisure and beyond. However, currently AR technologies are let down by the performance of microdisplays. AR devices must operate successfully not only in darkened rooms but also in bright sunlight, and must also be very small and run all day on one charge of a compact battery. Hence, enormous demands are placed on tiny light emitters in microdisplays in terms of brightness and efficiency. For AR to become a mass market technology, any new approach to microdisplays will need to not only meet these demands, but also allow easy manufacturing. Current light emitting diodes (LEDs) fail to meet these needs, since key materials which work well for larger area light emitters exhibit a drop in efficiency when the device size is shrunk to meet the demands of form factor and resolution imposed by AR. However, in terms of large scale LEDs, devices based on gallium nitride (GaN) have been tremendously successful, transforming the lighting industry. GaN LEDs also show much lower drops in efficiency with reduction in size than other similar materials. Unfortunately, these GaN LEDs are highly efficient only for light emission in the blue region of the spectrum. Green, amber and particularly red devices based on the same materials have much lower efficiencies, but are needed to create full colour microdisplays. In white LED light bulbs, blue light is converted to other colours by phosphor materials, but these phosphors are manufactured as bulky micron sized powders, too coarse to be used in microLEDs. In this project, we will take a new approach to integrating alternative, nanometre-scale phosphor particles (ca. 100 atoms wide) with nitride LEDs. Our alternative phosphors are highly luminescent colloidal nanoparticles, synthesised straightforwardly in solution using scalable techniques and easily made into nanoparticle inks. These materials are already used in "QLED" display technologies, but display manufacture is complex and the difficulties increase substantially as the device shrinks. Our new concept is to use printing technologies to inject nanoparticles not onto the surface of LEDs, but into nanoscale pores in the GaN itself. The nanoporous GaN materials are a very recent development and unique, scalable methods for their fabrication have been invented in our laboratory. By printing onto these porous scaffolds we will exploit capillary action to suck the nanoparticles into the desired region of the device, preventing spreading of the nanoparticle ink and hence achieving controlled manufacture straightforwardly at the required scale. In so doing, we will create a new optical composite material - a combination of the GaN and the highly luminescent nanoparticles - and by using the structure of the nanopores to align and control the array of nanoparticles, we will enable new and more sophisticated devices, for future display technologies such as AR in three dimensions.

The use of colour in every consumer product is ubiquitous. However with increasing concern for the environment, the use of traditional dyes is becoming problematic. This has opened up new opportunities in producing colour by carving out materials at scales smaller than a millionth of a metre, built of components which are benign. In addition, the new possibilities available for structural colours (iridescent, prismatic, multi-hue, or luminescent) are universally attractive in competitive marketplaces such as mobile electronics, fashion, and automotive/airline industries.We have invented a new process for making plastic films which have appealing structural colours, that can be scaled up to industrial production levels. It is based on making periodic arrangements of stacked nano-spheres with a different optical density to their surroundings, called 3D photonic crystals. Until now, there has been no way to make industrial-scale cheap photonic crystals. Our method is based on making plastic sphere precursors which can be heated and extruded together in such a way that they slide over each other into perfectly packed arrays. By adding tiny nano-particles (hundreds of times smaller in size) in between the spheres we can make an enormous variety of new sorts of materials or fibres which have 'smart' colour. For instance, the films are elastic and they drastically change colour when they are stretched, or are bent.In order to realise the possibilities in our discoveries, we need to find out how to properly control this shearing-assembly of polymer nanoparticles, by testing out the extrusion on a reasonable scale while measuring optically how it is taking place. We also need to develop ways to extrude fibres that could be used for making iridescent fabrics. Only when we understand the mechanisms in detail will we know enough to scale up production to the level that industry wants to see before investing further in commercial manufacture. We can also make a variety of even more intriguing films, including ones which glow with different colours, or are magnetic. We also need to show how the films might decompose to see what environmental issues might be raised by releasing such material on a widespread basis. Finally we need to develop a plan for which particular applications that we should concentrate on, in collaboration with a number of large companies.Everyone who we show these rubbery iridescent films to, wants a piece to take away with them. We want to be able to provide films to everyone, by commercialising our nanomaterials research and development.