Search results for "ELECTROLUMINESCENCE"
showing 10 items of 128 documents
Efficient electroluminescence from a perylenediimide fluorophore obtained from a simple solution processed OLED
2009
Simple solution processed organic light emitting diodes are used to screen the performance of two types of highly efficient, narrow band red emitting fluorescent perylenediimides (PDIs). PDIs substituted at the diimide positions seem to form aggregates in the thin film architecture as evidenced by the shifted electroluminescent spectrum. When substituted on the bay position and when used both as the emitting and the electron transporting specie, bright electroluminescence with a narrow width around 610 nm reaching 500 cd m−2 at moderate voltages was observed, demonstrating the usefulness of these fluorophores for OLED applications.
Deep-blue thermally activated delayed fluorescence (TADF) emitters for light-emitting electrochemical cells (LEECs)
2017
The authors acknowledge the University of St Andrews for financial support. The authors also acknowledge financial support from the European Union H2020 project INFORM (grant 675867), the Spanish Ministry of Economy and Competitiveness (MINECO) via the Unidad de Excelencia María de Maeztu MDM-2015-0538, MAT2014-55200 and the Generalitat Valenciana (Prometeo/2016/135). MLP acknowledges support from a Grisolia grant (GRISOLIA/2015/A/146). Two deep blue thermally activated delayed fluorescence (TADF) emitters ( imCzDPS and imDPADPS ) that contain charged imidazolium groups tethered to the central luminophore were designed and synthesized as small molecule organic emitters for light-emitting e…
Bright and stable light-emitting electrochemical cells based on an intramolecularly π-stacked, 2-naphthyl-substituted iridium complex
2014
The synthesis and characterization of a new cationic bis-cyclometallated iridium(III) complex and its use in solid-state light-emitting electrochemical cells (LECs) are described. The complex [Ir(ppy)2(Naphbpy)][PF6], where Hppy = 2-phenylpyridine and Naphbpy = 6-(2-naphthyl)-2,2′-bipyridine, incorporates a pendant 2-naphthyl unit that π-stacks face-to-face with the adjacent ppy− ligand and acts as a peripheral bulky group. The complex presents a structureless emission centred around 595–600 nm both in solution and in thin film with relatively low photoluminescence quantum yields compared with analogous systems. Density functional theory calculations support the charge transfer character of…
Green light-emitting devices based on soluble oligo(phenylenevinylenes)
2005
In this work, we report our investigations on the film-forming properties as well as the optical and electroluminescent characterisations of a series of lateral-substituted soluble oligo(phenylenevinylenes) of various conjugation length. Preliminary investigations show that these materials are potential candidates for use in organic light-emitting devices (OLEDs). Two types of OLEDs were fabricated: single layer (SL) and single heterostructure (SHS), with poly(p-phenylenevinylene) (PPV) as hole transporting layer. Our best results were obtained with single layer device emitting green light with a luminance of 0.18 cd m(-2) and 0.24 cd m(-2) at a driving voltage of 10 V. (c) 2004 Elsevier B.…
Light-emitting diodes based on phenylenevinylene oligomers with defined chain lengths
1997
Abstract We present characteristic electroluminescence data on single-layer devices based on three different oligo phenylenevinylene compounds with defined chain lengths. Light-emitting diodes (LEDs) were prepared by subsequent vacuum evaporation of the oligomer film and the A1 top electrode onto an indium—tin oxide (ITO) substrate. The LEDs show light emission in the spectral range of yellow to orange depending on the conjugation length of the compound used. We report photoluminescence and optical absorption data of the thin sublimed films, together with the wavelength dependence of the electroluminescence and with the current—voltage characteristics of the LED devices. The redox behavior …
Electron drift properties in high pressure gaseous xenon
2018
[EN] Gaseous time projection chambers (TPC) are a very attractive detector technology for particle tracking. Characterization of both drift velocity and di¿usion is of great importance to correctly assess their tracking capabilities. NEXT-White is a High Pressure Xenon gas TPC with electroluminescent ampli¿cation, a 1:2 scale model of the future NEXT-100detector, which will be dedicated to neutrinoless double beta decay searches. NEXT-White has been operating at Canfranc Underground Laboratory (LSC) since December2016. The drift parameters have been measured using 83mKr for a range of reduced drift ¿elds at two di¿erent pressure regimes, namely 7.2 bar and 9.1 bar. Theresults have been comp…
Energy resolution studies for NEXT
2011
This work aims to present the current state of simulations of electroluminescence (EL) produced in gas-based detectors with special interest for NEXT --- Neutrino Experiment with a Xenon TPC. NEXT is a neutrinoless double beta decay experiment, thus needs outstanding energy resolution which can be achieved by using electroluminescence. The process of light production is reviewed and properties such as EL yield and associated fluctuations, excitation and electroluminescence efficiencies, and energy resolution, are calculated. An EL production region with a 5 mm width gap between two infinite parallel planes is considered, where a uniform electric field is produced. The pressure and temperatu…
Increasing the efficiency of light-emitting electrochemical cells by limiting the exciton quenching
2013
ABSTRACTLight-emitting electrochemical cells (LECs) are one of the simplest electroluminescent devices. The possibility to be processed from solution and to operate with air-stable materials makes them an attractive alternative to organic light emitting diodes (OLEDs). Still their efficiencies are below those obtained in OLEDs. Additionally the best efficiencies were reported at low luminances and sustained for a short period of time. Here we show that for a LEC employing an orange-emitting charged iridium complex that is driven using a pulsed driving scheme high efficiencies of up to 20.5 cd A-1 can be obtained at high luminance and sustained over the device lifetime. It is also shown that…
Influence of mobile ions on the electroluminescence characteristics of methylammonium lead iodide perovskite diodes
2016
In this work, we study the effect of voltage bias on the optoelectronic behavior of methylammonium lead iodide planar diodes. Upon biasing the diodes with a positive voltage, the turn-on voltage of the electroluminescence diminishes and its intensity substantially increases. This behavior is reminiscent of that observed in light-emitting electrochemical cells (LECs), single-layer electroluminescent devices in which the charge injection is assisted by the accumulation of ions at the electrode interface. Because of this mechanism, performances are largely independent from the work function of the electrodes. The similarities observed between planar perovskite diodes and LECs suggest that mobi…
Ionization and scintillation response of high-pressure xenon gas to alpha particles
2013
High-pressure xenon gas is an attractive detection medium for a variety of applications in fundamental and applied physics. In this paper we study the ionization and scintillation detection properties of xenon gas at 10 bar pressure. For this purpose, we use a source of alpha particles in the NEXT-DEMO time projection chamber, the large scale prototype of the NEXT-100 neutrinoless double beta decay experiment, in three different drift electric field configurations. We measure the ionization electron drift velocity and longitudinal diffusion, and compare our results to expectations based on available electron scattering cross sections on pure xenon. In addition, two types of measurements add…