Smart thermochromic windows whose insulation properties are tuned by the ambient temperature have been investigated extensively over recent years to improve energy efficiency of commercial and residential buildings. These windows are typically coated with thermochromic materials that exhibit a fully reversible, temperature dependent transition between semiconductor and metallic phases. During hot weather, a smart window passes all or part of the visible radiation incident and rejects the majority of the Sun's near-infrared radiation; thus the need for air conditioning is reduced. During cooler weather, both visible and infrared (IR) radiation is fully transmitted, limiting the need for internal heating. A popular material for such intelligent coatings is Vanadium dioxide (VO2) due to i) the radiation stop-band manifesting in the IR region, ii) the advantage that it can easily be applied to large substrates and iii) the ability to lower its phase transition temperature by doping it with metal compounds, most commonly tungsten. Calculations have shown that a VO2 coating can deliver a 30% reduction in energy consumption of buildings in countries with hot climates such as Italy and Egypt. Nonetheless, the merits of VO2 coatings quickly diminish in colder climates and in places like Helsinki or Moscow they, in fact, deliver a negative energy balance. One very important factor for this performance reversal is the high refractive index that VO2 exhibits in its cold-transparent phase, which results in a large portion of the incident light being reflected - 30%-35% in the visible for a 50 nm thick VO2 film on glass. This figure compares with <4% reflectivity in conventional glass windows, meaning that a thermochromic window is much darker and colder than its plain glass counterpart in the winter, which in turn translates to an actual increase in the energy required for lighting and heating a building. In addition, dirt and stains further degrade the transmission properties of a smart window. In order to overcome the above limitations, moth-eye type structures engineered to exhibit broadband and wide-angle antireflection properties are proposed, for the first time, to substantially improve the currently poor transmission properties of thermochromic smart windows and to pave the way for the commercialization of this technology. Our nanopatterned windows potentially have 72% higher transmission compared to existing thermochromic windows and in addition, they exhibit simultaneous self-cleaning properties without additional processing. This challenging, proof-of-concept, 24-month research project focuses on the fabrication and characterization of smart windows enhanced with moth-eye nanostructures and is divided into two research streams: A) Fabrication and characterization of antireflection and self-cleaning moth-eye nanostructures directly onto glass, appropriate for new high-end window products. B) Development of potentially low-cost thermochromic polymer thin-film to retrofit existing non-smart windows.

New optoelectronically and photonically active materials - such as organic semiconductors and nanoparticles - are bringing to market new technologies and products such as organic light-emitting diodes (OLEDs) and new phosphors (as used in QD TVs and LED white lighting). Our understanding of the fundamental properties of these materials as well as the rate of design of new materials is accelerating. Of particular interest is a new generation of systems combining organic semiconductors with inorganic nanoparticles. These hybrid blends or nanocomposites hold great promise as a platform technology for high-efficiency low-cost solar energy harvesting devices, photodetectors and novel LEDs for displays, communications and chemical diagnostics. A scalable manufacturing process for these materials will rely on solution processing of an ink comprising the organic semiconductor, the nanoparticles and a suitable solvent to produce a functional film or coating. However, the components of these organic-nanoparticle blends have a strong tendency to aggregate and phase separate during solution processing, due to a mismatch of their size, shape and surface energies1. This severely compromises device performance and to date has ruled out the manufacture of these systems via large-area-compatible solution manufacturing techniques such as bar-coating, slot-die coating or inkjet printing. Our proposed methodology will overcome these problems, demonstrating routes by which the two active components spontaneously self-assemble during deposition and subsequent solvent evaporation to yield a nanocomposite with a precise morphology and structure over the hierarchy of length scales described above. Thus, our proposal directly tackles the challenge of achieving the precision manufacture at scale of functional nanocomposites. We seek to develop new molecular engineering methodologies providing a toolkit of manufacturing approaches enabling precise control over a hierarchy of length scales. This will create manufacturing routes a new generation of optoelectronically and photonically active coatings and films based on organic-nanoparticle blends, accelerating the translation of fast-moving developments in the physics and chemistry of these hybrid materials into economic benefit for the UK and benefits to society world-wide.

This project is centred on the development of the materials, device structures, materials processing and PV-panel engineering of excitonic solar cells (ESCs). These have the potential to greatly reduce both materials and also manufacturing costs where the materials, such as organic semiconductors, dyes and metal oxides, can be processed onto low-cost flexible substrates at ambient temperature through direct printing techniques. A major cost reduction is expected to lie in much-reduced capital investment in large scale manufacturing plant in comparison with conventional high vacuum, high temperatures semiconductor processing. There are extensive research programs in the UK and India developing these devices with the objective of the increase in PV efficiency through improved understanding of the fundamental processes occurring in these optoelectronic composites. However, there has been less activity in the UK and India on establishing from this science base a scalable, commercially viable processing protocol for excitonic solar cells. The scope of this UK-India call enables research and development to be undertaken which can pull together the set of activities to enable manufacturing application, and this extends beyond the usual scope of funding schemes accessible to the investigators. This project tackles the challenge to create cost-effective excitonic solar cells through three components: new material synthesis of lower cost materials; processing and development of device (nano)architectures compatible with low process costs; and the scale up towards prototypes which can replicate solar cell performance achieved in the research phase. The team includes leading scientists in the UK and India working on excitonic solar cells. Skills range from material synthesis and processing, device fabrication and modelling, wet processing of large area thin films, and PV panel manufacture and testing. Careful consideration has been made to match and complement the skills on both sides of the UK-India network. Further to this, engagement with industrial partners in both the UK and India will allow access to new materials, substrates etc., and access to trials and testing of demonstration PV panels in the field.

This project is centred on the development of the materials, device structures, materials processing and PV-panel engineering of excitonic solar cells (ESCs). These have the potential to greatly reduce both materials and also manufacturing costs where the materials, such as organic semiconductors, dyes and metal oxides, can be processed onto low-cost flexible substrates at ambient temperature through direct printing techniques. A major cost reduction is expected to lie in much-reduced capital investment in large scale manufacturing plant in comparison with conventional high vacuum, high temperatures semiconductor processing. There are extensive research programs in the UK and India developing these devices with the objective of the increase in PV efficiency through improved understanding of the fundamental processes occurring in these optoelectronic composites. However, there has been less activity in the UK and India on establishing from this science base a scalable, commercially viable processing protocol for excitonic solar cells. The scope of this UK-India call enables research and development to be undertaken which can pull together the set of activities to enable manufacturing application, and this extends beyond the usual scope of funding schemes accessible to the investigators. This project tackles the challenge to create cost-effective excitonic solar cells through three components: new material synthesis of lower cost materials; processing and development of device (nano)architectures compatible with low process costs; and the scale up towards prototypes which can replicate solar cell performance achieved in the research phase. The team includes leading scientists in the UK and India working on excitonic solar cells. Skills range from material synthesis and processing, device fabrication and modelling, wet processing of large area thin films, and PV panel manufacture and testing. Careful consideration has been made to match and complement the skills on both sides of the UK-India network. Further to this, engagement with industrial partners in both the UK and India will allow access to new materials, substrates etc., and access to trials and testing of demonstration PV panels in the field.

The world is currently undergoing one of the biggest transformations in energy usage since the industrial revolution. From the poorest to the richest nations, our planet has shown the consequences of climate change, and the exhaustion of some fossil fuels is now in the foreseeable future. We have started to change the way we generate, distribute and use energy throughout the world. Solar power is one of the most environmentally favourable sources, which in principle could provide all the energy required for the planet. Solar cells use the photovoltaic effect to convert solar energy to usable electrical energy, and thus are a key technology to provide the world with renewable, inexpensive and reliable electricity. Photovoltaics research and industry have experienced enormous advancements in the last two decades. The most important material by far in the photovoltaics field is silicon. Silicon today accounts for over 85 % of the photovoltaics market, and has over 140 GW of installed capacity. Current silicon solar cell systems have an energy payback time of only 2-4 years with 30-years lifetime. Their cost of power generation is now falling below 0.5 $/W, and in some areas of the world they are already cost effective for supplying grid electricity. Silicon photovoltaics is therefore an extremely promising technology where significant technological improvements are still possible which will ensure further price reductions and increased deployment. Silicon solar cells capture solar energy when light is absorbed near the cell's surface and it creates electrical charge carriers. These carriers then diffuse through the cell, get collected at one of the contacts and are then able to deliver electricity. In this process many carriers are lost due to the imperfections of the material. The conversion efficiency of a solar cell is therefore limited by this loss of charge carriers at imperfections and defects. The surface of the cell represents a major material defect. The reduction of charge loss at the surface, termed passivation, is hence a critical feature requiring improvement. This project aims to improve the efficiency of silicon solar cells by optimising passivation using the cost-effective technologies proposed and patented as part of my previous research work. It is rare that a newly proposed technique could produce a step-change in the efficiency of passivation in commercial solar cells. This grant application will specifically enable that step-change to be developed. My research programme includes the fabrication, processing and characterisation of different passivation coatings used in solar cell manufacture. Different methods of producing the coatings and enhancing their passivation properties will be studied. Techniques to deposit the coating will include chemical and physical vapour deposition. In each case the key importance will be the characteristics of the layer with respect to storing excess electric charge that will be especially introduced. The research will be carried out at the Oxford Materials department, in close partnership with four UK manufacturing companies and a leading overseas research centre, the Fraunhofer Institute for Solar Energy Systems ISE. This institute will provide processing and characterisation facilities, staff time and state-of-the-art custom-made solar cells, and will also help interface the outcomes of this collaboration to the solar cell industry worldwide. Overall, this project will combine a strong team of academics and industry to improve efficiency and reduce the cost of semiconductor solar cells, thus paving the way for wide deployment and uptake of a technology with the potential to provide the world with abundant renewable and reliable energy.