Strongly-coupled microcavities are a fascinating system for the exploration of the fundamental physics of the interactions between light and matter. Under such circumstances, the emissive states in such microcavities are termed 'polaritons', and can be described as an admixture between an exciton and a confined cavity photon. The optical properties of polaritons can be very different from their constituent parts (excitons and cavity photons), and thus there is a significant opportunity to explore new fundamental processes, and develop new types of devices that may find applications as low-threshold lasers, optical-amplifiers and high-speed optical switches. At present, the majority of work done on the strong-coupling regime in microcavities has centred on structures that contain inorganic semiconductors (either III-V, II-VI or GaN based materials). We have however pioneered the study of strong-coupled microcavities containing organic (carbon-based) semiconductors, which are anticipated permit new effects to be engineered. Despite the importance of organic-semiconductors in a range of optoelectronic devices (LEDs, photovoltaics, FETs, lasers etc) relatively little is understood regarding the microscopic processes that occur in strongly-coupled organic microcavities.Development of a basic understanding of non-linear processes and properties of organic-semiconductors in strongly-coupled microcavities will thus be a key area that we will address in this project. Key components of the research include studies the interactions between organic-polaritons and vibrational modes of the molecular semiconductor and the generation of organic exciton-polaritons at high density following electrical injection of carriers. We will also explore the fabrication and optical properties of 'hybrid-semiconductor' microcavities and devices (containing organic and inorganic semiconductors), and will study optically-driven energy-transfer between the different types of excitation using both linear and ultra-fast measurements. We are confident that our work will provide new fundamental insights into the optical properties of organic-polaritons (including relaxation and condensation), the transfer of excitations between different semiconductor materials via a cavity photon over large distances (> 100 nm) and the generation of new electrically-driven polariton devices. We believe that we are in an excellent position to undertake such an ambitious programme of research due to our world-leading expertise in strongly coupled organic semiconductor microcavities (Sheffield), and two-colour ultra-fast spectroscopy of microcavities (Southampton).

Large-Area Electronics is a branch of electronics in which functionality is distributed over large-areas, much bigger than the dimensions of a typical circuit board. Recently, it has become possible to manufacture electronic devices and circuits using a solution-based approach in which a "palette" of functional "inks" is printed on flexible webs to create the multi-layered patterns required to build up devices. This approach is very different from the fabrication and assembly of conventional silicon-based electronics and offers the benefits of lower-cost manufacturing plants that can operate with reduced waste and power consumption, producing electronic systems in high volume with new form factors and features. Examples of "printed devices" include new kinds of photovoltaics, lighting, displays, sensing systems and intelligent objects. We use the term "large-area electronics" (LAE) rather than "printable electronics" because many electronic systems require both conventional and printed electronics, benefitting from the high performance of the conventional and the ability of the printable to create functionality over large-areas cost-effectively. Great progress has been made over the last 20 years in producing new printable functional materials with suitable performance and stability in operation but despite this promise, the emerging industry has been slow to take-off, due in part to (i) manufacturing scale-up being significantly more challenging than expected and (ii) the current inability to produce complete multifunctional electronic systems as required in several early markets, such as brand enhancement and intelligent packaging. Our proposed Centre for Innovative Manufacturing in Large-Area Electronics will tackle these challenges to support the emergence of a vibrant UK manufacturing industry in the sector. Our vision has four key elements: - to address the technical challenges of low-cost manufacturing of multi-functional LAE systems - to develop a long-term research programme in advanced manufacturing processes aimed at ongoing reduction in manufacturing cost and improvement in system performance. - to support the scale-up of technologies and processes developed in and with the Centre by UK manufacturing industry - to promote the adoption of LAE technologies by the wider UK electronics manufacturing industry Our Centre for Innovative Manufacturing brings together 4 UK academic Centres of Excellence in LAE at the University of Cambridge (Cambridge Integrated Knowledge Centre, CIKC), Imperial College London (Centre for Plastic Electronics, CPE), Swansea University (Welsh Centre for Printing and Coating, WCPC) and the University of Manchester (Organic Materials Innovation Centre, OMIC) to create a truly representative national centre with world-class expertise in design, development, fabrication and characterisation of a wide range of devices, materials and processes.

Hybrid polaritonics combines the properties of different light emitting materials - organic polymers and semiconductors - in order to produce quasiparticles that combine the possibilities of both systems. "Polaritons" are quasi-particles that arise from strong coupling between light and matter. This means that they have hybrid properties, combining the mobility and flexibility of light, with the possibilities of interactions due to the matter component. At high enough densities, or low enough temperatures, polaritons can form a macroscopic coherent quantum state, a polariton condensate, or a polariton laser. Such a coherent state shows much of the same physics as Bose Einstein Condensation, as has been seen for cold atoms, but without requiring the ultra-low tempeatures required for atoms. Hybid polaritonics focuses on how, by combining different "matter" parts of the polariton, one can push these temperatures even higher, up to room temperature, and how one can engineer completely tunable system. The matter part of a polariton can come from any material which will absorb and emit light at a specific wavelength. Much existing work on polaritons is based on the material being inorganic semiconductors. These can be grown controllably, and one can drive such devices by passing an electrical current through them to make a polariton laser. However, the coupling between matter and light in semiconductors is not strong enough for these devices to work at room temperature. In contrast, organic molecules and polymers can show huge coupling strengths, but are generally poor electrical conductors. Our programme is to combine the benefits of both systems to provide a whole set of devices, operating at room temperature, based on the formation of polaritons. These devices will range from polariton lasers (providing a route to easily tunable lasers with very low threshold currents), to Terrahertz light sources (with applications in non-invasive medical imaging and explosives detection), to ultra-efficient light emitting diodes. To reach these ambitious objectives, we need to combine expertise from a wide number of fields. Our team contains world experts in light emitting polymers, semiconductor growth, characterisation and spectroscopy of polaritons, and in theoretical modelling. Members of our team have previously achieved the first realisations of polariton lasing, of strong coupling with organic materials, and of building hybrid polariton lasers. The possibility to combine this expertise draws on the unique strengths that the UK currently has in this area, and enables the combination of this expertise to be focussed on providing room temperature devices based on hybrid polaritonics, and to revolutionise this field.

This project is clearly focused on understanding one of the most fundamental aspects of organic light emitting devices, which as yet is little recognised as being so important. With CDT we have shown that up to 37% of light coming from an OLED device arises from triplet fusion, in itself an absolutely fundamental excitonic process which if not at all well understood. By elucidating the triplet fusion mechanism and demonstrating that 0.50 singlet yield is possible with correct triplet energy levels we aim to build devices that could attain internal quantum efficiencies of 0.62 from fluorescent emitters. This would provide a real step change in OLED performances both for displays and lighting. Together with CDT we shall work to develop a new device architecture to fully exploit this possibility. This will be a highly adventurous piece of applied science. We will also collaborate with Kyushu University on small molecule systems in evaporated devices. A range of state of the art spectroscopic techniques will be used, most developed in and unique to Durham, to fully elucidate the photophysical process underpinning triplet triplet annihilation and triplet fusion, some of the most fundamental excitonic processes in organic materials but still poorly understood. We will determine how singlet yield from triplet fusion is controlled by energy levels of the molecule. Further, we shall also determine the efficiency of upper excited state triplet inter system crossing to the singlet manifold, a further process which we believe also contributes to the overall singlet yield both in an optical experiment and in an OLED device. Together with CDT will will develop a novel device based on a polymer dyad where triplet fusion is maximised and aim to produce fluorescent OLEDs with efficiencies approaching those of phosphorescent devices. In this way we can produce blue fluorescent devices of high efficiency without the short lifetime associated with phosphorescent systems. This would be a major step change for OLED device. This project has the full support of Cambridge Display Technology who will provide £45,000 to off set the EPSRC cost of the project and another £30,000 in new materials developed specifically for this project and further resource for modelling and project management.

In inorganic semiconductors, such as silicon, the interaction of electronic excitations with lattice vibrations is an undesirable perturbation; it limits charge carrier mobilities and mediates non-radiative recombination. In low-dimensional functional materials with non-covalent bonding the structural dynamics is not a mere perturbation, it moves centre-stage: Some vibrational modes are very soft and strongly anharmonic so that electronic processes occur in a strongly fluctuating structural landscape. The traditional view is that the resulting strong electron-vibrational coupling is also detrimental: In organic semiconductors (OSCs), for example, electronic charges and neutral electron-hole pairs (excitons) are localized by a 'cloud' of lattice deformations, which causes charge mobilities and exciton diffusion lengths to be undesirably small, thus limiting performance of optoelectronic devices. We have recently discovered systems in which this traditional paradigm does not hold, but in which the structural dynamics is highly beneficial and mediates surprisingly fast, long-range excitation transport. This runs completely against models developed for traditional semiconductors such as silicon, for which phonons limit electronic transport. The mechanism involves vibrational modes coupling localized states near the band edges to highly delocalised states within the bands that can then transport charges and energy over unprecedentedly long length scales. This unique transient delocalization regime, in which excitations are effectively able to "surf on the waves" of structural lattice distortions, is not found in silicon and was first discovered in OSCs. Our goal is to explore similar physics in other functional materials with soft structural dynamics, such as hybrid organic-inorganic perovskite (HOIP) semiconductors, 2D conjugated covalent/metal organic frameworks (COFs/MOFs) and inorganic ceramics and ion conductors. VISION AND AMBITION: In the proposed programme we aim to pursue this vibration-enhanced transport (VET) regime as a general paradigm for achieving fast and long-range electronic charge, ion and energy transport in a broad class of organic and inorganic, functional materials with soft structural dynamics. We will (i) develop new experimental/theoretical methodologies to achieve a deep fundamental understanding of the underpinning mechanisms for the vibration-enhanced transport, including identification and molecular engineering of the most effective vibrational modes mediating it, (ii) design new self-assembled functional materials in which transport length scales exceeding micrometers are achievable and (iii) exploit such long length scales to enable new device architectures and transformational device performance improvements in a broad range of (bio)electronic, optoelectronic, energy storage and photocatalytic applications.