Search results for "Electroluminescence"

Luminescent osmium(II) bi-1,2,3-triazol-4-yl complexes: photophysical characterisation and application in light-emitting electrochemical cells

2016

The series of osmium(II) complexes [Os(bpy)3-n(btz)n][PF6]2 (bpy = 2,2’-bipyridyl, btz = 1,1’-dibenzyl-4,4’-bi-1,2,3-triazolyl, 1 n = 0, 2 n = 1, 3 n = 2, 4 n = 3), have been prepared and characterised. The progressive replacement of bpy by btz leads to blue-shifted UV-visible electronic absorption spectra, indicative of btz perturbation of the successively destabilised bpy-centred LUMO. For 4, a dramatic blue-shift relative to the absorption profile for 3 is observed, indicative of the much higher energy LUMO of the btz ligand over that of bpy, mirroring previously reported data on analogous ruthenium(II) complexes. Unlike the previously reported ruthenium systems, heteroleptic complexes 2…

Photonic-crystal silicon-nanocluster light-emitting device

2006

We report on enhanced light extraction from a light-emitting device based on amorphous silicon nanoclusters, suitable for very-large-scale integration, and operating at room temperature. Standard low-cost optical lithography is employed to fabricate a two-dimensional photonic crystal onto the device. We measured a vertical emission with the extracted radiation enhanced by over a factor of 4, without the aid of any buried reflector. These achievements demonstrate that a cost-effective exploitation of photonic crystals is indeed within the reach of semiconductor industry and open the way to a new generation of nanostructured silicon devices in which photonic and electronic functions are integ…

Electroluminescence and transport properties in amorphous silicon nanostructures

2006

We report the results of a detailed study on the structural, electrical and optical properties of light emitting devices based on amorphous Si nanostructures. Amorphous nanostructures may constitute an interesting system for the monolithic integration of optical and electrical functions in Si ULSI technology. In fact, they exhibit an intense room temperature electroluminescence (EL), with the advantage of being formed at a temperature of 900 °C, while at least 1100 °C is needed for the formation of Si nanocrystals. Optical and electrical properties of amorphous Si nanocluster devices have been studied in the temperature range between 30 and 300 K. The EL is seen to have a bell-shaped trend …

Amplified Spontaneous Emission Properties of Solution Processed CsPbBr3 Perovskite Thin Films

2017

Metal halide perovskites are currently emerging as highly promising optoelectronic materials. It has been recently demonstrated that fully inorganic solution processed CsPbBr3 perovskite thin films show good electroluminescence properties combined with high thermal stability. In this work, we investigate in details the amplified spontaneous emission (ASE) properties of CsPbBr3 perovskite thin films, as a function of the temperature and the trap density, modified by changing the CsBr-PbBr2 precursor concentration. ASE is observed in samples from both CsBr-rich solution (low trap density) and equimolar solution (higher trap density), up to about 150 K, with a minimum threshold of 26 and 29 mu…

Soret emission from water-soluble porphyrin thin films: effect on the electroluminescence response

2009

The emission properties of TSPP [tetrakis(4-sulfonatophenyl) porphyrin] and TMPyP [tetrakis(4-methylpyridyl) porphyrin] in thin films, prepared both by the Langmuir–Blodgett technique and the spin-coating method, have been investigated. Surprisingly, in most of the samples analyzed, the emission spectra do not show the usual two bands typical of porphyrins (in the region 650–750 nm), and depend strongly on the excitation energy. The origin of a new emission band detected at ∼480–500 nm is discussed in terms of the nature of the porphyrin aggregates. Moreover, we demonstrate that the presence or absence of this band in the fluorescence spectrum is directly related to the generation of electr…

A semiempirical correlation between the optical band gap of hydroxides and the electronegativity of their constituents

2000

In analogy with previous results on anhydrous oxides, a correlation is proposed between the optical band gap of hydroxides and the electronegativities of their constituents. Based on the experimental results on passive hydrated layers on metals obtained in our laboratory and the literature data, it is found that the hydroxide band gap varies with the square of the difference between the electronegativities of the metallic cation and the hydroxyl group. Like in the case of anhydrous oxides, two different interpolation lines have been found forsp-metal andd-metal hydroxides, respectively. The proposed correlations predict semiconducting or insulating behavior even for the most electronegative…

Highly Stable and Efficient Light-Emitting Electrochemical Cells Based on Cationic Iridium Complexes Bearing Arylazole Ancillary Ligands.

2017

A series of bis-cyclometalated iridium(III) complexes of general formula [Ir(ppy)2(N∧N)][PF6] (ppy− = 2-phenylpyridinate; N∧N = 2-(1H-imidazol-2-yl)pyridine (1), 2-(2-pyridyl)benzimidazole (2), 1-methyl-2-pyridin-2-yl- 1H-benzimidazole (3), 2-(4′-thiazolyl)benzimidazole (4), 1- methyl-2-(4′-thiazolyl)benzimidazole (5)) is reported, and their use as electroluminescent materials in light-emitting electrochemical cell (LEC) devices is investigated. [2][PF6] and [3][PF6] are orange emitters with intense unstructured emission around 590 nm in acetonitrile solution. [1][PF6], [4][PF6], and [5][PF6] are green weak emitters with structured emission bands peaking around 500 nm. The different photoph…

Deciphering the Electroluminescence Behavior of Silver(I)‐Complexes in Light‐Emitting Electrochemical Cells: Limitations and Solutions toward Highly …

2019

Long-Living Emitting Electrochemical Cells Based on Supramolecular π-π Interactions

2009

AbstractThe complex [Ir(ppy)2(dpbpy)][PF6] (Hppy = 2-phenylpyridine, dpbpy = 6,6'-diphenyl-2,2'-bipyridine) has been prepared and evaluated as an electroluminescent component for light-emitting electrochemical cells (LECs). The complex exhibits two intramolecular face-to-face π-stacking interactions and long-lived LECs have been constructed; the device characteristics are not significantly improved in comparison to analogous LECs with 6-phenyl-2,2'-bipyridine with only one π-stacking interaction.

Air stable hybrid organic-inorganic light emitting diodes using ZnO as the cathode

2007

An air stable hybrid organic-inorganic light emitting device is presented. This architecture makes use of metal oxides as charge injecting materials into the light emitting polymer, avoiding the use of air sensitive cathodes commonly employed in organic light emitting diode manufacturing. We report the application of zinc oxide as a cathode in an organic light emitting device. This electroluminescent device shows high brightness levels reaching 6500 cd/m2 at voltages as low as 8 V. Compared to a conventional device using low workfunction metal cathodes, our device shows a lower turn-on voltage and it can operate in air.