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In 1985, fac-Ir(ppy)3 was characterised as the first triply ortho-metalated iridium(III) species. This bright yellow solid exhibits green phosphorescent emission. Since then, numerous related iridium(III) complexes of the formula Ir(L)3 and Ir(L)2acac have been synthesised utilising ligands such as 2-phenylpyridine (ppy), 4-(2-pyridyl)benzaldehyde (fppy), benzo[h]-quinoline (bzq) and 2-(2-thienyl)pyridine (thpy), to name, but a few. These complexes give rise to tuneable emission wavelengths via ligand modification and also exhibit electroluminescence allowing them to be used as phosphorescent dopants in Organic Light Emitting Devices (OLEDs), the next generation of flat panel displays. In this work, ortho-metalating ligands, especially substituted 2-phenylpyridines, have been produced by a variety of synthetic pathways. The subsequent cyclometalating reactions of these ligands with iridium(III) and rhodium(III) have afforded a series of complexes whose photophysical properties can be related in part to the substituents upon the ligands. In general, these complexes exhibit phosphorescent emission that is derived from an excited metal to ligand charge transfer state (MLCT), which possesses mostly triplet character. Emission from this triplet excited state to the ground state is formally forbidden. However, strong spin-orbit coupling provides mixing of the 3MLCT state with higher energy singlet states thus' providing this transition with intensity. Long lifetimes and oxygen-quenched emission are therefore typical of these complexes. Tuning the emission wavelength of these complexes is possible by altering the relative energy of the emissive 3MLCT state and is achieved by altering the substituents that reside upon the cyclometalating ligands. The reversible oxidation of these complexes under anaerobic conditions has also been demonstrated. For these iridium(III) complexes the position of the oxidative wave follows a pattern in which more positive values are found for complexes of ligands bearing electron-withdrawing substituents and less positive values result from ligands with electron-donating substituents. Studies of polymer films doped with these iridium(Ill) complexes have shown efficient energy transfer between the host and guest species. This is inferred by the lack of host emission even at doping concentrations as low as 0.5 % wt. /wt. This is vital if these compounds are to be used as electroluminescent dopants in OLEDs.

A comparison of phosphor preparation methods was carried out. Scanning electron microscopy (SEM), X-ray diffraction (XRD) and photoluminescence measurements were used to evaluate the methods. The most suitable for DC electroluminescence (DCEL) was found to be a thioacetamide synthesis. The DCEL forming process was investigated using Laser-Raman spectroscopy. This showed no changes in copper concentration in the formed layer of a DCEL device following the forming process, suggesting that the forming process may be due to oxidation. Indium tin oxide (ITO) conductive-coated plastic was used successfully as a replacement for ITO-coated glass in DCEL devices and methods were developed for the use of cross-linked linseed oil as a binder in DCEL panels, producing a very flexible phosphor/binder layer. The feasibility of producing infra-red emitting electroluminescent devices for particular applications was investigated. ZnCdS: Cu layers were incorporated into DCEL, and ACEL devices. The DCEL devices showed a strong photoelectric effect. The ACEL devices produced infra-red emission. Further investigation of the photoelectric effect in DCEL and ACEL devices was carried out and work functions were determined for a variety of systems.

Les plasmons polaritons de surface (SPPs) jouent un rôle central en nanophotonique, parce que ce sont des modes optiques qui peuvent être confinés dans l’espace à l’échelle de 10 nm et dans le temps à l’échelle de 10 fs. L’excitation électrique des plasmons polaritons de surface par effet tunnel inélastique peut être ultrarapide et localisée, ce qui permet de développer une nanosource pour la nanophotonique intégrée en profitant pleinement du potentiel des polaritons plasmon de surface. Pourtant, ce processus est très inefficace avec un rendement de conversion typique de 10-7~10-5 plasmon par électron.Dans ce manuscrit de thèse, nous présentons une étude théorique et expérimentale qui vise à augmenter l’émission de plasmons de surface par effet tunnel inélastique avec une nano-antenne résonante. Nous avons développé un modèle théorique pour décrire l’émission de lumière à partir d’une jonction à effet tunnel en utilisant le théorème de fluctuation-dissipation. Nous proposons deux stratégies pour augmenter le rendement de conversion électron-plasmon. Nous introduisons un mode d’antenne résonnante confiné à l’échelle du nanomètre afin de renforcer le couplage entre le courant et le champ. En outre, nous introduisons l’hybridation d’un mode plasmonique metal/isolant/metal confiné et d’un mode d’antenne. Nous prédisons théoriquement que 30% de l’énergie émise par un dipôle est sous forme de SPP pour une longueur d’onde de travail de 800nm et une épaisseur d’isolant de 1 nm.Nous avons développé les processus de fabrication pour réaliser les antennes à effet tunnel en utilisant la configuration Al/AlOx/Au. L’antenne fabriquée présente une fonctionnalité robuste concernant les propriétés électriques et optiques. Nous montrons l’antenne permet de contrôler le spectre d’émission SPP, la polarisation d’émission SPP et renforcer l’efficacité des émissions de SPP de plus de 3 ordres de grandeur. La puissance totale émise sous forme de SPP est de l’ordre de 10 pW, quatre ordres de grandeur de plus que la puissance typique émise par une pointe de microscope à effet tunnel. / Surface plasmon polaritons (SPPs) plays a central role in nanophotonics because they are optical modes that can be confined in space at the 10 nm scale and in time at the 10 fs scale. Electrical excitation of surface plasmon polaritons by inelastic tunneling electrons has the potential to be fast and localized so that it offers the opportunity to develop a nanosource for on-chip nanophotonics taking advantage of the full potential of surface plasmons polaritons. However, inelastic tunneling is rather inefficient with a typical electron-to-plasmon conversion efficiency of 10-7~10-5. In this thesis manuscript, we present a study for enhancing surface plasmon emission by inelastic tunneling electrons with a resonant nanoantenna. It consists of theoretical and experimental investigations. First, we have developed a theoretical model to describe the light emission from a tunnel junction based on the fluctuation-dissipation theorem. Second, we have theoretically demonstrated two strategies to improve the antenna SPP efficiency thus aiming to enhance electron-to-plasmon conversion efficiency. We introduce a resonant antenna mode with a sub-nanometer gap in order to enhance the coupling between the inelastic current and the the mode. Furthermore, we introduce the hybridization in a nanopatch antenna between a gap mode and an antenna mode to launch SPPs: we theoretically predict that 30% of the power emitted by a dipole is converted into SPP (working wavelength at 800nm) with a 1nm gap thickness. Third, we have developed the fabrication procedures to realize antenna tunnel junctions based on the Al/AlOx/Au configuration. The fabricated antenna junction shows a robust functionality both regarding electrical and optical properties. The antenna junction is demonstrated to control the SPP emission spectrum, the SPP emission polarization and enhance the SPP emission efficiency by over 3 orders of magnitude. The total SPP power emitted is in the range of 10 pW, four orders of magnitude larger than the typical fW power emitted by a scanning tunneling tip junction.