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Highly luminescent poly(arylene vinylene)s can be prepared by a range of polycondensation methods. In this paper we report the synthesis of useful monomers and their application in the Gilch dehydrohalogenation and Wittig polycondensation methods to prepare highly luminescent poly(1,4-phenylene vinylene) (PPV) homo- and copolymers for use in light emitting devices.

We have used electroabsorption measurements as non-invasive probes of the built-in potential of polymer light-emitting diodes (PLEDs). Such measurements provides precious experimental information on the alteration of the polymer/electrode interfacial energy level line-up.

Controlling the nanoscale arrangement in polymer-fullerene organic solar cells is of paramount importance to boost the performance of such promising class of photovoltaic diodes. In this work, we use a pseudo-bilayer system made of poly(2,5-bis(3-hexadecylthiophen-2-yl)thieno[3,2-b]thiophene (PBTTT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM), to acquire a more complete understanding of the diffusion and intercalation of the fullerene-derivative within the polymer layer. By exploiting morphological and structural characterisation techniques, we observe that if we increase the film solidification time the polymer develops a higher crystalline order, and, as a result, it does not allow fullerene molecules to intercalate between the polymer side-chains. Gaining insight into the detailed fullerene intercalation mechanism is important for the development of organic photovoltaic diodes (PVDs).

We investigate, for the first time, the effect of signal clipping on multi-band carrier-less amplitude and phase (m-CAP) modulation in visible light communications based on PLEDs. We experimentally demonstrate a Q-factor improvement up to ~2.25 dB can be obtained with a clipping level of 50%.

The semiconducting-polymer/injecting-electrode heterojunction plays a crucial part in the operation of organic solid state devices. In polymer light-emitting diodes (LEDs), a common fundamental structure employed is Indium-Tin-Oxide/Polymer/Al. However, in order to fabricate efficient devices, alterations to this basic structure have to be carried out. The insertion of thin layers, between the electrodes and the emitting polymer, has been shown to greatly enhance LED performance, although the physical mechanisms underlying this effect remain unclear. Here, we use electro-absorption measurements of the built-in potential to monitor shifts in the barrier height at the electrode/polymer interface. We demonstrate that the main advantage brought about by inter-layers, such as poly(ethylenedioxythiophene)/poly(styrene sulphonic acid) (PEDOT:PSS) at the anode and Ca, LiF and CsF at the cathode, is a marked reduction of the barrier to carrier injection. The electro- absorption results also correlate with the electroluminescent characteristics of the LEDs.

The energy gap law (EG-law) and aggregation quenching are the main limitations to overcome in the design of near-infrared (NIR) organic emitters. Here, we achieve unprecedented results by synergistically addressing both of these limitations. First, we propose porphyrin oligomers with increasing length to attenuate the effects of the EG -law by suppressing the non-radiative rate growth, and to increase the radiative rate via enhancement of the oscillator strength. Second, we design side chains to suppress aggregation quenching. We find that the logarithmic rate of variation in the non-radiative rate vs. EG is suppressed by an order of magnitude with respect to previous studies, and we complement this breakthrough by demonstrating organic light-emitting diodes with an average external quantum efficiency of ~1.1%, which is very promising for a heavy-metal-free 850 nm emitter. We also present a novel quantitative model of the internal quantum efficiency for active layers supporting triplet-to-singlet conversion. These results provide a general strategy for designing high-luminance NIR emitters., Light-emitting diodes: Near-infrared fluorescence from organic molecules Organic (carbon-based) light-emitting diodes (LEDs) that emit near-infrared light can be built by linking together large organic molecules called porphyrins, offering many potential industrial and medical applications. Organic near-infrared LEDs have several advantages over conventional LEDs based on inorganic semiconductors, including mechanical flexibility, biocompatibility and the absence of polluting heavy metals. Researchers in the UK and Italy led by Harry Anderson at the University of Oxford and Franco Cacialli at University College London explored the potential of linked porphyrin structures that fluoresce at near-infrared wavelengths. The optical properties of the materials are improved by engineering the molecular structure and a quantitative model is presented to explain the efficient emission. This research provides understanding of exciton dynamics and points towards innovative uses of near-infrared light in applications including light therapy, optical communications, biosensors and biometric systems.

This paper is concerned with making and manipulating conjugated polymers and studying their properties, particularly their behaviour when incorporated as the active components of a field effect transistor/electro–optic switch or a light emitting diode device structure. Two examples will be discussed. In the first we will show how the Durham precursor route to polyacetylene can be manipulated via the use of living polymerization techniques using well defined Schrock ROMP initiators to produce a self–ordering polyene precursor which gives significantly improved charge carrier mobilities and device performance. The second topic discussed will concern recent work on the application of McMurray coupling to the synthesis of electroluminescent poly(arylene vinylene)s.

The synthesis of poly(1,4-phenylene vinylene)s (PPVs) containing a 2,3-dialkoxy substitution pattern has been developed. Poly[2,3-bis(2-ethylhexyloxy)-1,4-phenylene vinylene)] (BEH-PPV, 4) was prepared and its optical properties compared with the recently discussed poly(2,3-dibutoxy-1,4-phenylene vinylene) (DB-PPV, 1), which showed in contrast to classical 2,5-substituted PPV derivatives a notable blue-shift of the longest-wavelength absorption (λmax) and a considerable increase of the solid-state photoluminescence (PL) efficiency. The two statistical PPV copolymers 5 and 6 comprising 2,3-dibutoxy and dimethyloctylsilyl- or 2,5-bis(dimethyloctylsilyl) side-chains, respectively, were synthesized via the Gilch dehydrohalogenation route. Double-layer light-emitting devices (LEDs) were demonstrated to combine high electroluminescence efficiencies with low turn-on voltages.

We studied the luminescence of microcavities consisting of a single-layer of poly(para-phenylenevinylene), PPV, sandwiched between a dielectric mirror coated with a conducting indium-tin oxide layer and a semi-transparent metal electrode. Compared with a device without cavity structure, the emission is spectrally and spatially narrowed, and the forward emission intensity enhanced. The Full Width at Half Maximum of the modes is about 4 nm in photoluminescence and we measure an enhancement of intensity in the forward direction of more than an order of magnitude. The PL efficiencies and lifetimes on a sub-ns time scale show only minor alterations with respect to PPV on glass.

We report the synthesis of novel alternating copolymers of the kind A-alt-B, where A is a dialkylfluorene unit and B is an aromatic moiety unit which is varied in order to change the position of the frontier energy levels; in particular we find that the B unit thiophene S,S-dioxide is particularly effective at increasing the polymer electron affinity and ionisation potential.

The first 10 Mb/s real-time organic visible light communications system based on polymer light-emitting diodes is demonstrated using a Virtex-6 FPGA-based LMS equalizer, with an improvement rate of 7 Mb/s compared to the current state-of-the-art.