Transparent conducting oxides (TCO) are ubiquitous in modern society, being components in a vast array of consumer electronics (e.g. smart phones, tablets, lap tops, flat panel displays etc.) and finding use in applications such as solar cells, smart windows, low emissivity windows etc. To date, the TCO with the largest share of the market is tin doped indium oxide (known as ITO), which displays excellent transparency and conductivity. The fact that indium is not very abundant in the earth's crust (and is often found in unstable geopolitical areas), allied to the inexorable increase in the demand for consumer electronics globally, has caused large fluctuations in the price of indium over the past decade. This has understandably caused concern in the industrial sector. Other TCO materials exist, such as fluorine doped tin dioxide (FTO), antimony doped tin dioxide (ATO), and Aluminium doped zinc oxide (AZO), however, they have not reached the performance levels of ITO. In each case, the limitations are linked to the dopant that is used Recently we proposed an initial understanding of how some specific novel dopants can produce enhanced performance TCOs, termed the "remote impurity scattering mechanism", and we will now screen novel dopants in the earth abundant host oxides zinc oxide, tin dioxide and barium stannate, in order to find the ideal TCO/dopant combination. This will be done in 3 ways: 1) Computational screening of novel dopants 2) Deposition of doped thin films using low cost, scaleable chemical vapour deposition 3) Physical characterisation of the doped films The synergistic approach between computational chemistry, semiconductor physics and low cost scaleable deposition will result in new high performance, low cost, industrially viable TCOs. They will be transferred from our labs to industrial scale processes on our project partner's float glass line.

Organic and other types of solution-processed solar cells are a highly promising alternative to conventional silicon-based photovoltaics (PV) as a lightweight, flexible, disposable and truly building-integrated PV technology with extremely quick energy payback. However, their limited stability has now been widely recognised as a common bottleneck for their commercialisation, with exposure to various environmental factors (e.g. light, heat, oxygen, humidity) leading to rapid losses of their performance, the origin of which often remains widely unclear. Fullerenes have been ubiquitously used as an electron acceptor and transport material in organic solar cells (OSCs) in the past two decades. Only until the last 3-4 years, non-fullerene acceptor materials have been brought to the forefront of the development of OSCs as a more efficient, lower-cost and more versatile alternative to fullerenes, with the performance of fullerene-free OSCs already significantly exceeding that of fullerenes-based OSCs. Nevertheless, the majority of research efforts to date have only been dedicated to further optimising their efficiency, leaving a clear gap in the understanding of their stability and degradation mechanisms, another key consideration for their commercialisation. This proposal is designed to address three very important yet largely unanswered questions in the development of stable fullerene-free OSCs: 1-What are the mechanisms causing the degradation of fullerene-free OSCs; 2-Can we understand these degradation mechanisms both comprehensively and quantitatively; and 3-What controls these degradation mechanisms and how to address them? To answer these questions, this proposal will develop a new research methodology to study OSC degradation, which has not been established previously. By performing time-resolved and inter-correlated optical, structural and functional analysis of PV films and devices degraded in a locally-controlled environment, this methodology is capable of capturing the real-time information of the fundamental processes leading to device performance losses during the degradation process, thereby establishing a quantitative relationship between the degradation mechanisms and the resulting OSC degradation behaviour. Specifically, the evolution (i.e. time-resolved) of several advanced, performance-determining device parameters, as well as that of chemical and structural changes during the same degradation process (i.e. inter-correlated), will be recorded and further analysed in order to reconstruct the OSC degradation behaviour. Only fullerene-free OSCs will be studied in this project, but the new methodology can be universally applied to study other types of solar cells, such as polymer:fullerene, quantum dots, dye-sensitised and perovskite solar cells. A core focus of this project is the quantitative analysis of the impacts of major degradation mechanisms of fullerene-free OSCs as a function of their material and device design. The PI has already led the research efforts in quantitatively investigating the degradation of fullerenes and their impacts upon OSC stability, which laid the foundations for the development of the new research methodology proposed here. Based on the quantitative knowledge acquired, this proposal also aims to develop comprehensive material and device design rules capable of guiding the systematic optimisation of the stability of fullerene-free OSCs. This proposal will build upon the established research expertise and facilities in energy materials and devices at Cardiff University, in close collaboration with Swansea University and Imperial College London. The project will be carried out in partnership with 1) Eight19 Ltd., a UK-based SME specialising in the commercialisation of OSC products; 2) NSG group, a UK-based, world-leading company in glass and glazing products (e.g. glass-based PV products) 3) Armor group, a France-based company specialising in printing and coating technologies.

Perovskite solar cells (PSCs) are solution processable, have high efficiencies and promise low cost renewable electricity. Unfortunately, the widespread application of PSCs is being held back by their poor long-term stability. Their established rivals, crystalline-silicon solar cells, offer a 25 year operational lifetime. However, high efficiency PSCs are operationally stable for less than 6 months. Perovskites have very low mechanical toughness due to the intrinsically low energy required to separate perovskite crystals. Solar cell operation lifetime increases with mechanical toughness and we aim to exploit this relationship to greatly enhance the stability of high efficiency PSCs. Taking inspiration from highly tough natural biomaterials (such as nacre) we will use synthetic analogues of adhesive proteins to glue the crystals together and increase perovskite mechanical toughness. Our new particles are ultra-deformable nanometre-sized gel particles (termed ultra-low crosslinked nanogels, ULC nanogels). Building on our earlier work where conventional nanogels improved lead-PSC stability, novel ULC nanogels will be prepared that conformally coat and interlink perovskite crystals. They will flatten to become ultra-thin and allow charges to move unhindered between crystals. We will also study lead-free, tin-perovskites and increase their operational stability by a combination of improvements in chemical stability and mechanical toughness. The link between the mechanical toughness and PSC stability will be investigated experimentally and using state-of-the-art modelling techniques. Modelling will also be used to study the energy changes involved in chemical degradation so as to establish materials design rules for PSCs with enhanced stability. A successful outcome to this project would provide improved fundamental understanding of the interplay between perovskite mechanical toughness and stability as well as a high efficiency demonstrator(s) with a projected operation lifetime of 8 years. Such a result would bring the large-scale deployment of perovskite photovoltaics for CO2-free electricity generation closer and increase energy security.

Energy consumed by buildings for heating, cooling, and lighting needs, accounts for more than 40% CO2 emissions. However, while keeping the thermal and visual comfort, a substantial portion of energy is lost due to our inability to control the ingress and egress of energy through transparent building envelope - mainly windows and facades. The UK government's ambitious target of reaching zero emission by 2050 cannot be achieved without controlling ingress and egress of energy through buildings. By 2050, 85% of the existing building stock will still be in use which indicates that retrofitting of building envelope is indispensable. Among the other building envelope, windows and facades are the least energy efficient but are easily replaceable. Glazing technology plays an important role in determining a building's energy performance, required to perform multiple roles of regulating heat transfer by conduction convection, solar and long wave radiation between internal and external environments while maintaining comfortable daylight environments by allowing the transmittance of natural daylight; reducing the need for supplementary electric lighting. The windows and facades also play an important aesthetic function by providing occupants a visual link to the external environment and influencing the appearance of buildings. Thus, developing new smart glazing technology for windows and facades to modulate the incoming and outgoing heat into indoor space to reduce building energy load, while at the same time providing visual comfort, is crucial. The proposed project aims to undertake an ambitious innovative research program of developing new technology to significantly reduce energy demand in the built environment at an acceptable cost. The goal will be achieved by reducing heat loss, controlling incoming solar radiation to maximise solar gain, minimise heat loss in winter and reverse it by flipping windows in summer while ensuring the best natural lighting conditions with no glare. The overarching goal of energy efficacy and visual comfort will be achieved by smart composite material in which each elements of composite will bring a unique property and contribute to enhance energy efficiency of windows and facades. In winter, the TIA will absorb external IR radiations and transfer heat to PCM for storage, which will be released back to the building, the TIM in composite will forbid heat loss through longwave thermal radiation and the IR reflective coating will prevent heat loss by reflecting IR back to room. In summer, the orientation will be flipped around to reduce cooling load. In the flipped case, heat gain by IR will be prevented by IR reflective layer while the TCM will regulator the transparency to control the indoor temperature constant. The multi-fold smart composite developed in this research program. This will enable advanced glazing technology to achieve U-values down to 0.4 W/m2K1 while maintaining comfortable daylight environments and reduce annual energy consumption by 30-40% for buildings. The outcome of this research will enable us to create technological pathways towards achieving energy positive buildings in the UK.

Evolution in device architectures have been central to the performance enhancements in all photovoltaic (PV) technologies. For silicon PV cells, they started as p-n junctions originating from the early p and n-doping studies in Bell Labs, USA, in the 1950s and have progressed to passivated interfaces with charge selective "heterojunctions" sandwiching homogeneously doped single crystal wafers. For metal halide perovskites, the early PV embodiments comprised perovskite nanocrystals "sensitizing" mesoporous TiO2 and have progressed to solid-perovskite absorber layers sandwiched between planar heterojunctions with increasingly well passivated interfaces. However, even a perfectly-passivated solar cell fabricated from a single solar absorber material has its limitations, with theoretical maximum solar-to-electric power conversion efficiencies topping out at 30%. The most popular route to circumvent these limitations is to create "multi-junction" or tandem solar cells, where more than one solar absorber material and device are stacked on top of each other, which leads to a theorised increase in efficiency to 45% for two junctions and over 50% for three junctions. The top runner for tandem cells is combining metal-halide perovskites with silicon, which have already demonstrated over 31% efficiency, and one of our partners, Oxford PV, is ramping up production of the first perovskite-on-silicon tandem technology. However, tandem cells are not the final word in PV efficiency. Our ambition is to carry out multidisciplinary research, via inter-linked work streams, that will explore and conceive new photovoltaic device concepts and paradigms, enabling the next major step-change in photovoltaic efficiency. We base our vision on two key questions; what do we predict to be the next game-changing transformation to PV technology? and what fundamental science and technical advances do we need to develop now, in order to deliver such a paradigm shift? We target 4 device concepts; * CONCENTRATOR PV, which operate under concentrated sun light to result in a 20 to 30% relative increase in power conversion efficiency as compared to "1-sun" operation technologies; * QUANTUM CUTTING, for which rare-earth doping of novel halide semiconductors can result in the generation of two low-energy photons for every high-energy photon absorbed, boosting the photocurrent generation in a PV device through photon-multiplication; * HOT-CARRIER COLLECTION, where carrier cooling losses are overcome by selectively extracting hot charge from a solar cell, boosting the theoretical efficiency limit all the way to 66%; * and a novel idea of a "PHOTON-TRANSPORT" cell, designed so that the majority of charges are transported to charge collection interfaces via photons, with the elimination of minority carriers from the bulk of the absorber negating internal recombination losses and enabling PV cells to reach their theoretical "radiative" limit. The PV absorber materials will be based on metal-halide perovskites, silicon, and novel low-band-gap chalcogenide-halide semiconductors designed and discovered in this project. Addressing these future advanced concepts through a holistic approach will enable us to make the first key scientific discoveries and important major technical advances in what will become the next generation of PV technologies for beyond 2030.