Organic light-emitting diodes have been fabricated using erbium tris(8-hydroxyquinoline) as the emitting layer and N, N′-diphenyl-N,N′-bis(3-methylphenyl)-1,1′-biphenyl-4,4′-diamine as the hole-transporting layer. Room-temperature electroluminescence was observed at 1.54 μm due to intra-atomic transitions between the I13/24 and I15/24 levels in the Er3+ ion. These results suggest a possible route to producing a silicon-compatible 1.54 μm source technology.

Samples of erbium (III) tris(8-hydroxyquinoline) (ErQ) have been prepared and their photoluminescence measured. Clearly resolved peaks due to intra-atomic transitions between the I413/2 and I415/2 levels can be observed at room temperature. The possibility of depositing ErQ on to silicon to produce organic electroluminescent diodes offers the possibility of a cheap 1.5 μm emitter based on silicon technology.

a ZnO is one of the most widely studied semiconductors due to its direct wide band gap and high exciton binding energy. Due to its ease of synthesis, robustness and low cost, ZnO has been applied in a wide range of devices, including nanogenerators, solar cells, and photodetectors. In this work, ZnO nanorods were synthesized in a single step using an aqueous method at temperatures below 100 1C. The nanorods were annealed in oxygen and nitrogen and a p-type polymer poly(3,4-ethylenedioxythiophene)polystyrene sulfonate (PEDOT:PSS) was spray coated onto the top of ZnO nanorods to form a p-n junction. The I-V characteristics of the device showed that the annealing atmosphere had a significant effect on the rectification ratio of the device. Further analysis using Mott-Schottky, photoluminescence, and X-ray photoelectron spectroscopy (XPS) indicated that oxygen vacancy concentration correlated well with the free electron density in ZnO as well as the rectification ratio of the p-n junction devices. Devices made with ZnO nanorods annealed in nitrogen had a better rectification ratio than oxygen, representing a simple method to improve p-n junction diode behaviour through tuning the defect properties of the nanorods via controlled annealing.

Radiative recombination mechanisms in aluminum tris(8-hydroxyquinoline): Evidence for triplet exciton recombination J. Appl. Phys. 88, 781 (2000) We have studied the photoluminescence and electroluminescence of neodymium tris-͑8-hydroxyquinoline͒ and have found evidence, from the Stark splitting of the neodymium emission, for two isomers of the molecule. Following sublimation it appears that one of these isomers predominates. Photoluminescence can be excited through absorption into the organic ligands and there appears to be efficient coupling between the singlet and triplet exciton levels in the ligand and the internal levels of the neodymium. We can obtain bright infrared electroluminescence from the intraatomic levels within the neodymium at wavelengths of 900, 1064, and 1337 nm.

We have used the interdiffusion of a multiple quantum well sample due to a thin source of vacancies, as a probe, to simultaneously measure the interdiffusion coefficient, diffusion coefficient for group III vacancies in GaAs and the background concentration of these vacancies in a single experiment. We have shown that the interdiffusion at all temperatures is governed by a constant background concentration of vacancies in the material and that this background concentration is the concentration of vacancies in the substrate material. The measured vacancy concentration is around 2ϫ10 17 cm Ϫ3 . This result shows that the vacancy concentrations inGaAs are not at thermal equilibrium concentrations as has been widely assumed. Rather it has value which is ''frozen in,'' probably at the GaAs crystal growth temperature. The activation energy found for the intermixing of InGaAs/GaAs is shown to be governed solely by the activation term for vacancy diffusion which is calculated to have an activation energy of 3.4Ϯ0.3 eV. ͓S0163-1829͑97͒05724-X͔

1.5-μm light-emitting diodes which operate at room temperature have been fabricated on silicon substrates. The devices use an erbium-containing organic light-emitting diode (OLED) structure which utilizes p++ silicon as the hole injection contact. The OLEDs use N, N′-diphenyl-N,N′-bis(3-methyl)-1,1′-biphenyl-4,4′-diamine as the hole transporting layer and erbium tris(8-hydroxyquinoline) as the electron conducting and emitting layer.

A strategy is reported for the controlled assembly of organic-inorganic heterostructures consisting of individual single-walled carbon nanotubes (SWCNTs) selectively coupled to single semiconductor quantum dots (QDs). The assembly in aqueous solution was controlled towards the formation of monofunctionalized SWCNT-QD structures. Photoluminescence studies in solution, and on surfaces at the single nanohybrid level, showed evidence of electronic coupling between the two nanostructures. The ability to covalently couple heterostructures with single particle control is crucial for the design of novel QD-based optoelectronic and light-energy conversion devices.

The photoluminescence of aluminum tris͑8-hydroxyquinoline͒ ͑AlQ͒ has been studied as a function of temperature and excitation wavelength. It was found that as the temperature and excitation energy is reduced the peak of the photoluminescence moves to longer wavelengths and broadens significantly. The photoluminescence spectra obtained at all temperatures and excitation energies can be deconvolved into three distinct peaks originating from three levels within the molecule. A rate-equation approach has been used to model the observed behavior and to obtain the relative lifetimes of the three processes responsible for the photoluminescence. From this we infer that at low temperatures and excitation energies the radiative recombination of triplet excitons is responsible for a significant amount of the photoluminescence of AlQ. It is this process which is responsible for the low energy tail seen in the photoluminescence of AlQ but which is not present in the electroluminescence.