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.

Demand for high density, integrated electronics has become a defining feature of modern technology. At its ultimate limit, nanotechnology can enable low-cost and highly scalable sensors, computing elements, and lighting. The industrial benefits are clear - in particular bottom-up fabrication allows for high-level functionality and huge production scale at low cost. As this production technique emerges from the laboratory and into industry, issues such as yield, heterogeneity, and functional parameter spread have emerged as a critical aspect for efficacy to be established in advanced nanomaterials. To date, no framework exists for studying inhomogeneity in functional nano-electronics. I will combine highly-scaled measurements with cutting-edge data techniques to establish a gold-standard methodology for functional nanotechnology development, enabling industrial take-up. This will build on experimental approaches that I have recently demonstrated, including machine-vision identification of nanomaterials and automated electronic and optical spectroscopy, alongside computational approaches for rapid and technique-independent re-identification of single nanoparticles. I will implement analytics which draw on existing population-study methods such as linear and multivariate correlation; a specific goal of this project is to translate advanced techniques from diverse fields including astrophysics and health research, and in particular apply Bayesian analysis for model identification and augmented intelligence (including machine learning methods) where appropriate. These methodologies will be developed to study cutting edge challenges in functional nanomaterials; starting with the development of lasers for chip-to-chip communication, and the production of an industrially relevant capability for single-particle nanotechnology characterisation. By bringing this methodology together with pick-and-place capability through project partners, this project will enable demonstration of extremely low-yield yet transformative devices based on novel nanotechnology, for sensing, telecommunication or quantum devices.

Automated, data-driven, and high-throughput experimentation is already revolutionising materials exploration and optimization. While great strides have been made in using this approach to optimize bulk properties of materials, functional nanomaterials remain poorly understood due to the complex and often non-linear relationship between material quality, geometry, and performance. In the first part of my fellowship, I have developed and demonstrated a unique experimental and statistical methodology to study individual nanomaterial performance at huge scale, with tens of thousands to millions of measurements. This has provided unique insight, robust statistical evidence, and industrially useful yield analysis. In the renewal period I will lead a world-class team to tackle urgent challenges in nanotechnology, namely scale-up for quantum photonic technologies, and ultra-high-throughput for novel materials. My program will draw on the expertise and capability of 10 international academic and industrial partners to maximise the impact of the research.