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Back-contact perovskite solar cells are fabricated by depositing methylammonium lead iodide perovskite into micron-sized grooves, with opposite walls of each groove being coated with either n- or p-type selective contacts. V-Shaped grooves are created by embossing a polymeric substrate, with the different charge-selective electrodes deposited onto the walls of the groove using a directional evaporation technique. We show that individual grooves act as photovoltaic devices, having a power conversion efficiency of up to 7.3%. By series-connecting multiple grooves, we create integrated micro-modules that build open circuit voltages up to nearly 15 V and power conversion efficiencies over 4%. The devices created are fully flexible, do not include rare metals, and are processed using techniques applicable to roll-to-roll processing.

Nickel oxide (NiO) and titanium dioxide (TiO2) charge-extraction layers are fabricated under a partial pressure of O2 from nickel and titanium metals using a reactive electron-beam evaporation process. Using such materials, inverted architecture perovskite solar cells incorporating a NiO hole-transport layer achieve power conversion efficiencies up to 15.8%, whilst standard architecture devices using a TiO2 electron-transport layer achieve a power conversion efficiency up to 13.9%. Critically, we find that such metal oxides can be deposited at high speed (nm s−1) and at low substrate-temperature, and do not require a high-temperature anneal step after deposition, making reactive electron-beam evaporation compatible with roll-to-roll processing on sensitive flexible polymeric substrates.

Limited work has been done to optimize the power sharing among base stations (BSs) while considering the topology of the cellular network and the distance-dependent power loss (DDPL) in the transmission lines. In this paper, we propose two power sharing optimization algorithms for energy-harvesting BSs: the max-flow (MF) algorithm and the min-cost-max-flow (MCMF) algorithm. The two proposed algorithms minimize the power drawn from the main grid by letting BSs with power surpluses transmit harvested power to BSs with deficits. The MCMF algorithm has an additional DDPL cost associated with each transmission line. Hence, the MCMF algorithm shares the harvested power over shorter distances and loses less power during the transmission than the MF algorithm. Our numerical results show that for a fully connected cellular network, i.e., every pair of BSs can share power, with a moderate power loss coefficient per ${l}\,\,{{(}{ {\in }}\,\,{\mathbb {R}}^{{+}}{)}}$ meters of transmission line, the MCMF algorithm saves up to 10%, 22%, and 30% more main grid power than the MF algorithm for 5, 10, and 15 BSs uniformly distributed in a square area of ${l^{2}}$ square meters, respectively.

In this paper, a systematic review of academic literature and policy papers since 2008 is undertaken with an aim of identifying the prevalent energy systems models and tools in the UK. A list of all referenced models is presented and the literature is analysed with regards sectoral coverage and technological inclusion, as well as mathematical structure of models. The paper compares available models using an appropriate classification schema, the introduction of which is aimed at making the model landscape more accessible and perspicuous, thereby enhancing the diversity of models within use. The distinct classification presented in this paper comprises three sections, which specify the model purpose and structure, technological detail and mathematical approach. The schema is not designed to be comprehensive, but rather to be a broad classification with pertinent level of information required to differentiate between models. As an example, the UK model landscape is considered and 22 models are classified in three tables, as per the proposed schema.

How to embed reflexivity in public participation in techno-science and to open it up to the agency of publics are key concerns in current debates. There is a risk that engagements become limited to “laboratory experiments,” highly controlled and foreclosed by participation experts, particularly in upstream techno-sciences. In this paper, we propose a way to open up the “participation laboratory” by engaging localized, self-assembling publics in ways that respect and mobilize their ecologies of participation. Our innovative reflexive methodology introduced participatory methods to public engagement with upstream techno-science, with the public contributing to both the content and format of the project. Reflecting on the project, we draw attention to the largely overlooked issue of temporalities of participation, and the co-production of futures and publics in participation methodologies. We argue that many public participation methodologies are underpinned by the open futures model, which imagines the future as a space of unrestrained creativity. We contrast that model with the lived futures model typical of localized publics, which respects latency of materials and processes but imposes limits on creativity. We argue that to continue being societally relevant and scientifically important, public participation methods should reconcile the open future of research with the lived futures of localized publics.

This article argues that the emphasis on solving substantive “real world” problems through\ud interdisciplinary research collaboration can neglect the wider value created by such collaborations.\ud Championing the role of a knowledge integration and reflection facilitator, the article contends that\ud more recognition be given to the value of ‘spillover’ effects associated with interdisciplinary modes\ud of working, rather than focusing solely on knowledge outputs and impacts. Drawing on embedded\ud research conducted in relation to a project on local energy futures involving physicists, architects\ud and geographers, the paper illustrates such ‘spillover’ in relation to academic practice in teaching,\ud project management; and research methods. Such spillovers signal that what travels in\ud interdisciplinary working is much more than formal knowledge and point to potential long term\ud legacy effects from interdisciplinary working, back in disciplines.

Cross-sectional TEM and SEM have been used to study the degradation of organic solar cells when exposed to a high humidity environment. Two obvious effects were caused by this exposure: voids at the aluminium/calcium interface and large bubble like protrusions on the top surface. Water ingress was found to occur mainly from the edge rather than through pinholes or defects in the aluminium film. The grain size of the aluminium used in the cathode was varied and small grained devices were found to have degraded faster. The importance of minimising water ingress into devices through cathode design and choice of materials is highlighted.

We configured a generic digital lock-in amplifier as a light intensity-modulated spectrometer for photovoltaic (PV) cells for intensity-modulated spectroscopy (IMS) up to 250 kHz. We performed IMS on a state-of-the-art bulk heterojunction (BHJ) organic PV (OPV) cell and introduced a new mode of IMS, wherein PV cells work under finite load, including maximum power point (MPP). Quantitative analysis supported by equivalent circuit simulations establishes MPP-IMS as favorable alternative to the commonly used intensity-modulated photovoltage/photocurrent spectroscopy (IMVS/IMPS) modes. Using IMS under finite load, we identify a high-frequency feature that is invisible in both IMPS and IMVS. The feature is ageing-related and becomes more prominent after long-term storage. We propose an extended equivalent circuit model that locates the origin of this feature at the BHJ itself and link it to diffusion of indium ions etched from the transparent electrode by the hole extracting PEDOT:PSS. Finally, we introduce a method to determine BHJ capacitance by IMS without absolute calibration of light intensity.

The development of processing routes to fabricate organic photovoltaic devices (OPVs) using non-halogenated solvents is a necessary step towards their eventual commercialisation. To address this issue, we have used Hansen solubility parameter analysis to identify a non-halogenated solvent blend based on a mixture of carbon disulphide and acetone. This solvent blend was then used to deposit a donor–acceptor polymer–fullerene thin-film that was then used as the active layer of bulk-heterojunction OPV. For the benchmark polymer:fullerene system PCDTBT:PC70BM, a power conversion efficiency of 6.75% was achieved; a 20% relative improvement over reference cells processed using the chlorinated-solvent chlorobenzene. Improvements in device efficiency are attributed to an increase in electron and hole conductivity resulting from enhanced fullerene crystallisation; a property that leads to enhanced device efficiency through improved charge extraction.

Photovoltaic (PV) cell powered base stations (BSs) have been widely considered for reducing the cellular network's environmental footprint in the future. An inherent challenge is to match the energy generation profile with the energy consumption profile. In this paper, we develop a Markov chain based algorithm to determine the optimal orientation angle of the PV cell for matching the two profiles, given the energy generation profile of the geo-location, the load profile of the BS and the battery capacity. We investigate the effects of different battery capacities on the optimized PV cell orientation angle for BSs located in a business district in London in summer. Our results show that the optimal orientation angle for a small battery capacity (10000 Joules at a small BS) is in the range from 35° to 60°, whereas a wider range from −50° to 60° could be chosen for a large battery capacity (50000 Joules at a small BS). This reveals that PV cell orientation angle optimization is more important for PV cell powered BSs with small battery capacities than for large battery capacities.

An inherent problem of solar-energy-powered-small-cell base stations (SBSs) is that the energy generation of the photovoltaic (PV) cell does not match the energy consumption of the SBS in time. In this paper, we propose optimizing the PV cell orientation angle to achieve a good match between the energy generation and consumption profiles on a daily time scale. The optimization is formulated as an integer linear programming problem. We also derive an expression for the correlation between the energy generation and consumption profiles to evaluate their general interaction independent of the exact PV cell or SBS deployment setup. The numerical evaluation of the proposed angle optimization in a business area in London in summer/winter shows that the optimal PV cell orientation in summer contradicts the conventional assumption of south facing being optimal in the northern hemisphere. Instead, a southwest orientation should be chosen in summer due to its ability to shift the energy generation peak toward the energy consumption peak in the afternoon at an SBS in central London. This is in accordance with the prediction given by our derived correlation between the solar energy generation and consumption profiles.

Making accurate and reliable measurements of solar irradiance is important for understanding performance in the photovoltaic energy sector. In this paper, we present design details and performance of a number of fibre optic couplers for use in irradiance measurement systems employing remote light sensors applicable for either spectrally resolved or broadband measurement. The angular and spectral characteristics of different coupler designs are characterised and compared with existing state-of-the-art commercial technology. The new coupler designs are fabricated from polytetrafluorethylene (PTFE) rods and operate through forward scattering of incident sunlight on the front surfaces of the structure into an optic fibre located in a cavity to the rear of the structure. The PTFE couplers exhibit up to 4.8% variation in scattered transmission intensity between 425 nm and 700 nm and show minimal specular reflection, making the designs accurate and reliable over the visible region. Through careful geometric optimization near perfect cosine dependence on the angular response of the coupler can be achieved. The PTFE designs represent a significant improvement over the state of the art with less than 0.01% error compared with ideal cosine response for angles of incidence up to 50°.

Despite the increasing interest in photovoltaic (PV) cell powered small-cell base stations (SBSs), it has not been sufficiently studied yet how different PV cell angles can be utilized to achieve a good match between the energy arrival and consumption at the SBS. This is especially important in an urban environment where cellular network operators often struggle to apply optimal angles to the PV cells due to implementation constraints or shadowing effects of surrounding buildings. We develop an energy generation, storage and consumption model of a PV cell powered SBS, which includes the effects of PV cell orientations. A linear optimization problem is derived to optimize the energy performance of the SBS throughout the day. The effects of different PV cell orientations on the green energy utilization are evaluated assuming deployment in London in summer and winter. Our results show that west orientated PV cells (45° misalignment to the southern direction) are preferred in London during summer, whereas south orientated ones are preferred during winter. This reveals that the PV cell orientation needs to be optimized for not only the location and weather of the SBS deployment site but also the network traffic distribution in time (or energy consumption profile) of the deployment location.

Sources of error in the performance of large ensembles of spatially distributed photovoltaic generators are investigated and reported. Errors are propagated to estimate uncertainty in modeled global tilted radiation and performance ratio ( PR ) for the typical UK generator. Uncertainties in generators’ azimuth and elevation lead to typical monthly errors of 4% and 1% on global tilted radiation and PR . Interpolation of global horizontal irradiance is affected by an average 5% monthly error and the conversion to the inclined plane leads to an estimated error from 7% to 8% on tilted radiation and PR . This prediction has been verified against a set of twenty pyranometers on the plane of the array deployed across the UK, which gauge a 6% monthly error. Mutual cancellations lower this value to 4% for annual periodicity. The estimated monthly error on interpolated global horizontal irradiance is half of the 10% error affecting widely-used Photovoltaic Geographical Information System (PVGIS), which experiences larger errors also on the inclined plane. The assessed uncertainties impact the net present value of the investment required for deploying a PV generator; such an impact has been quantified. The yearly PR for the typical UK microgenerator is 84%, a value 8% (6%) higher than recent studies in France (Belgium). In winter, the typical UK performance ratio drops to 75%, because of an increase in shading. Summer performance ratio remains greater than the yearly mean, possibly reflecting the relatively short intervals during which direct sunlight heats the PV modules and the windy conditions over the British Isles. The monthly/annual error affecting the typical individual generator virtually cancel out for the whole national ensemble.

Polymer bulk heterojunction solar cells have been constructed using a thin film molybdenum oxide (MoOx) hole extraction layer that was fabricated by thermally annealing an ammonium molybdate tetrahydrate precursor layer deposited in air by ultrasonic spray-coating. Onto this layer was spray cast a PCDTBT:PC71BM film that acted as the active light-harvesting and charge-transporting layer. We optimise the processing steps used to convert the spray-cast MoOx precursor and show that the temperature at which it is annealed is critical to achieving high device efficiency as it both facilitates the removal of trapped solvent as well as driving its chemical conversion to MoOx. We demonstrate that by optimising the spray-casting and annealing process, we are able to create solar cell devices having a peak power conversion efficiency of 4.4%.

We report the use of ultra-sonic spray-coating under ambient conditions as a deposition technique for the fabrication of planar heterojunction CH3NH3PbI3−xClx perovskite solar cells. We make a first optimization of processing parameter space using this deposition technique, and explore the role of the temperature of the substrate during spray-casting, the volatility of the casting solvent and the post deposition anneal on determining the efficiency of the resultant solar cells. We find that maximum device efficiency is correlated with the creation of dense films having a surface coverage above 85%. When such films are incorporated into a solar cell device, power conversion efficiencies of up to 11% are realized. These results demonstrate that spray-coating can be used in the large-area, low-cost manufacture of high efficiency solution-processed perovskite solar cells.

Bulk heterojunction solar cells containing molybdenum oxide hole extracting anode contacts have been fabricated with varying stoicheometry using radio frequency reactive sputtering from a Molybdenum metal target. A blend of the newly synthesised conjugated polymer poly[9-(heptadecan-9-yl)-9H-carbazole-2,7-diyl-alt-(5,6-bis(octyloxy)-4,7-di(thiophen-2-yl)benzo[c][1,2,5]thiadiazole)-5,5-diyl] (PCDTBT-8) and fullerene [6,6]-Phenyl-C71-butyric acid methyl ester (PC70BM) was used as the photoactive layer and device results show that anodes with greater than 98% Molybdenum (VI) oxide result in peak power conversion efficiencies of 3.7%.The presence of up to 28% of Mo (V) results in no significant reduction in efficiency, however the presence of metallic Mo (IV) and lower oxidation states lead to severe reductions in device performance due to a combination of a large hole extraction energy barrier of approximately 0.9eV and reduced device stability.

In the present work we quantify the light intensity reaching the side faces of an externally-coated, rectangular luminescent solar concentrator, and the facets of a cylindrical one. Ray-tracing is used: an analytical model has been constructed and discretized. The main novelties reside in the attribution of a finite thickness and attenuation coefficient to the external layer, and in the comparison between two geometries that have been measured against each other only in the homogeneous limit so far. In previous studies the external material is usually treated as infinitely thin. A physical thickness allows, instead, to calculate the ray-paths, to quantify the absorption losses and to evaluate the efficiency of the concentrator as function of the external layer depth. A set of numerical experiments has been performed, in order to evaluate the efficiency of the concentrator when the thickness and material properties of the outer layer are changed, and to compare the performance of the rectangular to the one of the cylindrical device under various conditions. Qualitatively we find the bilayer device to have greater optical efficiency than a comparable homogenous version. For the cylindrical geometry the factor of improvement over the homogenous device is more strongly dependent on both the thickness and the attenuation of the luminescent layer than for the rectangular geometry.

We report the fabrication of high performance organic solar cells by spray-coating the photoactive layer in air. The photovoltaic blends consist of a blend of carbazole and benzothiadiazole based donor–acceptor copolymers and the fullerene derivative PC70BM. Here, we formulate a number of photovoltaic inks using a range of solvent systems that we show can all be deposited by spray casting. We use a range of techniques to characterize the structure of such films, and show that spray-cast films have comparable surface roughness to spin-cast films and that vertical stratification that occurs during film drying reduces the concentration of PCBM towards the underlying PEDOT:PSS interface. We also show that the active layer thickness and the drying kinetics can be tuned through control of the substrate temperature. High power conversion efficiencies of 4.3%, 4.5% and 4.6% were obtained for solar cells made from a blend of PC70BM with the carbazole-based co-polymers PCDTBT, P2 and P1. By applying a low temperature anneal after the deposition of the cathode, the efficiency of spray-cast solar-cells based on a P2:PC70BM blend is increased to 5.0%. Spray coating holds significant promise as a technique capable of fabricating large-area, high performance organic solar cells in air.

In this article we present a detailed comparison of ultrasonic spray coating and spin coating for the fabrication of polymer organic light-emitting diodes (OLEDs). Single-carrier devices of hole-transporting polymer poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(4,4’(N-(4-sec-butylphenyl))) diphenylamine] (TFB) were fabricated by ultrasonic spray coating. Uniform reference devices using spin coating were also made. We have shown, across a range of device thicknesses from 37 nm to 138 nm, typical of those used in OLED hole-transport layers, that there is no statistical difference in the hole-injection efficiency between ultrasonic spray coating and spin coating. We have also demonstrated the importance of controlling the roughness of the films and we determine a threshold of 10 nm average roughness below which injection efficiency is not controlled by roughness. However, above 10 nm roughness we find a reduction in injection efficiency up to an 86 % loss in performance for roughnesses of the order of 40 % the thickness of the film. By optimising the deposition parameters, in order to allow the wet films to start to equilibrate, we find a wide processing window for smooth uniform films with excellent injection efficiency. This work reinforces the importance of ultrasonic spray coating as a potential route to high volume manufacturing of OLED based technology.

The error in making a mean field approximation when analysing space charge limited currents in organic light emitting diodes has been assessed. Using a Poole Frenkel-like, exp ( γ E ) , field dependent mobility, space charge limited currents have been simulated using zero field mobilities from 10 −10 m 2 /V s to 10 −4 m 2 /V s and field dependent parameter γ from 10 −7 (m/V) 0.5 to 10 −2 (m/V) 0.5 . The simulated current–voltage data has been fitted using a mean field approximation to a modified Mott–Gurney equation and the deviation of zero field mobility and γ from the real values has been calculated. It was found that for a significant range of the simulations the error in both the zero field mobility and the γ factor was invariant, but systematically underestimated by 2% and 15% respectively. We conclude that the mean field approximation is a useful method with which to assess mobility using space charge limited currents in organic semiconductor devices, but the accuracy of such an analysis can be improved by accounting for the systematic error.

Low-temperature solution-processable vanadium oxide (V2Ox) thin films have been employed as hole extraction layers (HELs) in polymer bulk heterojunction solar cells. V2Ox films were fabricated in air by spin-coating vanadium(V) oxytriisopropoxide (s-V2Ox) at room temperature without the need for further thermal annealing. The deposited vanadium(V) oxytriisopropoxide film undergoes hydrolysis in air, converting to V2Ox with optical and electronic properties comparable to vacuum-deposited V2O5. When s-V2Ox thin films were annealed in air at temperatures of 100 °C and 200 °C, OPV devices showed similar results with good thermal stability and better light transparency. Annealing at 300 °C and 400 °C resulted in a power conversion efficiency (PCE) of 5% with a decrement approximately 15% lower than that of unannealed films; this is due to the relative decrease in the shunt resistance (Rsh) and an increase in the series resistance (Rs) related to changes in the oxidation state of vanadium.

We have developed a patterning procedure based on laser-ablation in combination with the use of water-soluble sacrificial-resists that we use to pixelate different light emitting polymers (LEPs) on a surface, creating a simple array of light emitting diodes (LEDs). We demonstrate that our patterning process is capable of high spatial resolution, with structures having a characteristic length-scale of 10 μm achieved. Importantly, we demonstrate that the patterning process has no detrimental effect on the electronic properties of the LEPs or of the underlying polymeric anode. Our process is compatible with a high-volume manufacturing environment and furthermore it could also be applied to pattern and integrate a wide range of functional polymeric materials for use in other applications.

We show that efficient nonradiative (Forster) energy transfer between solid films of two highly luminescent perylene dyes blended in a solid film can be used to control the amplified spontaneous emission (ASE) emitted from the films under pulsed optical excitation. Perylene orange, which acts as the donor, and perylene red, which is the acceptor, are doped into a host matrix of poly(methylmethacrylate) (PMMA). We report the ASE behavior as a function of acceptor concentration, and observe a sudden change in the spectral position of the ASE at an acceptor:donor concentration of 1:9 by weight. Below this concentration, emission is at 590 nm, which is characteristic of ASE from undoped perylene orange:PMMA blends, whereas films with higher acceptor concentrations produced ASE spectra centered at 620 nm, which is characteristic of perylene red:PMMA blends. In order to understand this behavior, the rate constant for energy transfer between the dyes was measured and found to be 5.0±0.2×1011 s−1 (mol/dm3)−1. We used this to deduce an upper limit for the stimulated emission rate of 4.9±0.2×108 s−1.

In this study the concentration quenching phenomenon is explored for seven organic singlet emitters (Rhodamine 6G, Pyridine 2, Lumogen F Red 305, Perylene, Coumarin 102, DCM and DCJTB) in an inert host of poly(methyl methacrylate) (PMMA). Combining fluorescence lifetime and quantum yield measurements on samples of different molecular separation allows a deep decay rate analysis to be performed yielding, for each fluorophore, a monomial power law that indicates the strength and type of interaction. The fluorophores studied exhibit interactions in between that of FRET-like dipole-dipole (R(-6)) and surface-surface (R(-2)) with many lying close to that expected for surface-dipole (R(-3)) interactions. With no observed dependence on molecular structure it is concluded that the concentration quenching rate in singlet emitters follows a power law as kCQ = aR(-3.1±0.7) with aggregation expected to increase the magnitude of the observed power.

The Forster energy transfer mechanisms in polyfluorene-based polymer blends have been investigated by picosecond time-resolved photoluminescence spectroscopy. Blends of poly(9,9-dioctylfluorene), (F8), and poly(9,9-dioctylfluorene-co-benzothiadiazole), (BT), ranging from 50% to 0.01% BT have been investigated from room temperature down to 12 K. In high concentration BT/F8 films, nearest neighbour transfers from F8 to BT, characterised by an F8 fluorescence lifetime of 12 ps, totally dominate. In low concentration BT/F8 films energy transfer between F8 and BT still occurs at nearest neighbour sites, but exciton migration to these sites amongst F8 chain segments now also contributes to the measured dynamics.

Diamond-like carbon (DLC) films with a range of sp(3) fractions have been examined by ultraviolet (UV) spectroscopy with 244 nm excitation. The UV Raman spectra of both hydrogenated and unhydrogenated films show the G peak near 1600 cm(-1) and a broad peak around 1200 cm(-1), which is attributed to C-C stretching vibrations of sp(3) sites. It is found that the ratio of the intensities of the C peak and the 1200 cm(-1) peak follows a universal dependence with the sp(3) content in both hydrogenated and unhydrogenated DLCs. This can be used for non-destructive evaluation of the sp(3) content of any DLC film.

The United Kingdom aims to decarbonize its national electricity generation in order to transition to a low carbon economy. Solar, wind, hydro and thermal energy conversion are renewable alternatives to fossil fuels and are currently being explored that may form part of the future generation mix of the country.How does materials scientist's work addressing energy research challenges for solar and storage (for example) translate into the adoption of new technology? How appropriate are the technology usage visions of the scientists? How can technology users better inform the materials science motivations? This report will focus on how a multidisciplinary team of researchers from the Universities of Sheffield and University of Durham, community members and industry representatives are jointly developing renewable energy projects to try to answer these and other questions. The history of the project will be presented as well as the methodology used to collaboratively engage the community participants.This work is supported by a grant provided by the Engineering and Physical Sciences Research Council (EPSRC) of the United Kingdom.

Recently, a new method has evolved for the recovery of materials in Waste Electrical and Electronic Equipment (WEEE) namely, the repurposing of constituent components for second life. Such an approach is opposed to the traditional raw materials harvesting that is the norm, which in the majority of cases leads to the destruction of serviceable parts together with all other non-recycling materials. This paper presents a novel photovoltaic system suitable for disparate population centres in the developing world utilising repurposed components from discarded computer power supplies.

To date, the recycling process for most Waste Electrical and Electronic Equipment (WEEE) simply involves recovering materials using pyrometallurgy and similar techniques due to the difficultly of removal of their constituent components. Thus most components are incinerated with all other non-recyclable materials. However, for specific types of WEEE an alternative approach has evolved namely the reuse or repurposing of particular parts of the equipment suitable for second life. This paper presents a novel photovoltaic system suitable for disparate population centers in the developing world utilising the ubiquitous ATX computer power supply.

The integration of organic light-emitting diodes (OLED) with state-of-the-art complementary metal oxide semiconductor (CMOS) drive electronics can yield a high-resolution full colour information display technology with superior viewing performance. Its application in consumer electronics is limited only by the desire of technology users to view information ‘near-to-eye’ with a magnifying lens. Unfortunately such a limitation is significant and the future prospect of OLED microdisplays looks confined to specialist applications. In this article the technical constraints of integrating two very different technology platforms, OLED and CMOS, are discussed. The experience of an eight year technology development programme, from technology concept to high volume manufacturing, is explored with specific issues relating to technology integration and manufacturing being discussed.

A rigorous measurement of the photoluminescence quantum yield (PLQY) of three luminescent solid state organic material systems is presented. Poly(9,9-dioctylfluorene), perylene (2.97 M in poly(methyl methacrylate)), and perylene red (0.78 M in poly(methyl methacrylate)), were measured using a Ti:sapphire laser yielding 47 ± 3%, 79 ± 3%, and 51 ± 2%, respectively. A GaN diode laser with differing variability was used to measure the PLQY for perylene and perylene red yielding 71 ± 1% and 53 ± 2%, respectively. Variations due to sample preparation (

Thin films of molybdenum oxide have been deposited by reactive magnetron sputtering and characterised by photoelectron spectroscopy. Such films of MoOx are increasingly being used as electrode interfaces in both organic light emitting diodes and bulk heterojunction polymer-fullerene solar cells. Control of the Mo to oxygen stoichiometry has been gained by two methods of R.F magnetron sputtering. The first method is by controlling the proportion of oxygen in the sputtering chamber and the second is by controlling the level of surface oxidation of the sputter target prior to deposition, both methods have been used to control average film stoichiometry. In general the transition from metallic like film to oxide like film occurs at an oxygen chamber partial pressure of 15 %. UPS measurements show that such a transition, and resulting increase in the average oxidation state, leads to a shift in the Fermi level from 4.5eV to 5.2eV with respect to vacuum. The presence of specific oxidation states below +6 give rise to electronic structures that lie between the valence band edge and the Fermi level. For reduced samples +2 and +5 oxidation states peaks appear at binding energies of 0.4eV and 2.1eV respectively while a third peak at 1eV could be attributed to either the presence of +3 or +4 oxidation states.

We introduce a new highly efficient photochromic organometallic dithienylethene (DTE) complex, the first instance of a DTE core symmetrically modified by two Pt(II) chromophores [Pt(PEt(3))(2)(C≡C)(DTE)(C≡C)Pt(PEt(3))(2)Ph] (1), which undergoes ring-closure when activated by visible light in solvents of different polarity, in thin films and even in the solid state. Complex 1 has been synthesised and fully photophysically characterised by (resonance) Raman and transient absorption spectroscopy complemented by calculations. The ring-closing photoconversion in a single crystal of 1 has been followed by X-ray crystallography. This process occurs with the extremely high yield of 80%--considerably outperforming the other DTE derivatives. Remarkably, the photocyclisation of 1 occurs even under visible light (>400 nm), which is not absorbed by the non-metallated DTE core HC≡C(DTE)C≡CH (2) itself. This unusual behaviour and the high photocyclisation yields in solution are attributed to the presence of a heavy atom in 1 that enables a triplet-sensitised photocyclisation pathway, elucidated by transient absorption spectroscopy and DFT calculations. The results of resonance Raman investigation confirm the involvement of the alkynyl unit in the frontier orbitals of both closed and open forms of 1 in the photocyclisation process. The changes in the Raman spectra upon cyclisation have permitted the identification of Raman marker bands, which include the acetylide stretching vibration. Importantly, these bands occur in the spectral region unobstructed by other vibrations and can be used for non-destructive monitoring of photocyclisation/photoreversion processes and for optical readout in this type of efficiently photochromic thermally stable systems. This study indicates a strategy for generating efficient solid-state photoswitches in which modification of the Pt(II) units has the potential to tune absorption properties and hence operational wavelength across the visible range.

We study the transitions between morphological phases of an oligofluorene (pentamer) thin-film using temperature-dependent photoluminescence emission. We find that the so-called β-phase can be created by cooling an amorphous thin-film to 80 K and then slowly returning it to room-temperature. This process is however suppressed if the thin-film is initially prepared in a poly-crystalline form. We also demonstrate that the presence of molecules in the β-phase suppresses the room-temperature crystallization that otherwise occurs in an amorphous film.

Summary from only given. Polymer blend systems have become increasingly important for use in organic light emitting diodes, offering improved device performance through balanced carrier injection and reduced self-absorption losses. In this work we present a detailed study of the dynamics of Forster energy transfer in commercially-important polyfluorene based polymer blend systems using time-resolved photoluminescence spectroscopy. We find that the conventional description based on the Forster radius is not readily applicable due to the poorly defined inter-molecule separation in the blend systems. By using the Langmuir-Blodgett technique to prepare layered nanostructures with precisely controlled host-guest separation, we have demonstrated accurately controllable transfer times and obtained improved understanding of the Forster processes in polymer blends.