The Experts below are selected from a list of 286227 Experts worldwide ranked by ideXlab platform
Kristiaan Neyts - One of the best experts on this subject based on the ideXlab platform.
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determining emissive dipole orientation in organic light emitting devices by Decay Time measurement
Organic Electronics, 2012Co-Authors: Lieven Penninck, Frank Steinbacher, Ralf Krause, Kristiaan NeytsAbstract:Abstract We present a method to detect anisotropy in the distribution of the transition dipole moment in organic light emitting diodes (OLEDs). The method is based on the dependency of the exciton Decay rate on the optical environment and the orientation of the dipole transition moment, also called the Purcell effect. We use this method to demonstrate a preferential orientation of the small molecule emitter Ir(MDQ) 2 (acac) in a TPBi matrix. The outcoupling improvement for OLEDs that could be obtained with perfectly oriented transition dipoles is estimated by simulation. For perfectly planar structures this shows an EQE in air of up to 34%.
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detailed analysis of exciton Decay Time change in organic light emitting devices caused by optical effects
Journal of The Society for Information Display, 2011Co-Authors: Saso Mladenovski, Sebastian Reineke, Lieven Penninck, Kristiaan NeytsAbstract:— The exciton Decay Time in organic light-emitting devices (OLEDs) depends on the optical environment, i.e., the thicknesses and refractive indices of all layers in a device. The Decay of an exciton can occur through a radiative or a non-radiative channel. Each of these channels has a probability, which is expressed by, respectively, the radiative and the non-radiative Decay rate. The radiative Decay rate is influenced by the optical environment, i.e., the OLED's thin-film layer structure. In this paper, a model for estimating the change of the exciton Decay Time (inverse of the Decay rate) is presented. In addition, the Decay Time change in both top- and bottom-emitting OLEDs as a function of the charge-transport layer thicknesses has been investigated. Furthermore, the most important mechanism responsible for the exciton Decay Time change is outlined.
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measurement and simulation of exciton Decay Times in organic light emitting devices with different layer structures
Optics Letters, 2009Co-Authors: Saso Mladenovski, Sebastian Reineke, Kristiaan NeytsAbstract:The Decay Time of an exciton depends on the coupling between the dipole oscillator and the optical environment in which it is placed. For an organic light-emitting device this environment is determined by the thin-film layer structure. The radiative Decay competes with nonradiative Decay channels and in this way influences the luminescent efficiency and the external quantum efficiency of the device. We describe a method to estimate the dependency of the exciton Decay Time and the luminescent efficiency on the thin-film stack and validate the results experimentally.
A I Mcleod - One of the best experts on this subject based on the ideXlab platform.
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hyperbolic Decay Time series
Journal of Time Series Analysis, 1998Co-Authors: A I McleodAbstract:Hyperbolic Decay Time series such as fractional Gaussian noise or fractional autoregressive moving-average processes exhibit two distinct types of behaviour: strong persistence or antipersistence. Beran (Statistics for Long Memory Processes. London: Chapman and Hall, 1994) characterized the family of strongly persistent Time series. A more general family of hyperbolic Decay Time series is introduced and its basic properties are characterized in terms of the autocovariance and spectral density functions. The random shock and inverted form representations are derived. It is shown that every strongly persistent series is the dual of an antipersistent series and vice versa. The asymptotic generalized variance of hyperbolic Decay Time series with unit innovation variance is shown to be infinite which implies that the variance of the minimum mean-square-error one-step linear predictor using the last k observations Decays slowly to the innovation variance as k gets large.
A V Baranov - One of the best experts on this subject based on the ideXlab platform.
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anomalous size dependent Decay of low energy luminescence from pbs quantum dots in colloidal solution
ACS Nano, 2012Co-Authors: Elena V Ushakova, Aleksandr P Litvin, Peter S Parfenov, A V Fedorov, M V Artemyev, A V Prudnikau, Ivan D Rukhlenko, A V BaranovAbstract:We report on an anomalous size dependence of the room-temperature photoluminescence Decay Time from the lowest-energy state of PbS quantum dots in colloidal solution, which was found using the transient luminescence spectroscopy. The observed 10-fold reduction in the Decay Time (from ∼2.5 to 0.25 μs) with the increase in the quantum dots’ diameter is explained by the existence of phonon-induced transitions between the in-gap state—whose energy drastically depends on the diameter—and the fundamental state of the quantum dots.
Stefan Kostler - One of the best experts on this subject based on the ideXlab platform.
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enabling luminescence Decay Time based sensing using integrated organic photodiodes
Analytical and Bioanalytical Chemistry, 2013Co-Authors: Martin Sagmeister, Bernhard Lamprecht, Andreas Tschepp, Elke Kraker, Tobias Abel, Torsten Mayr, Stefan KostlerAbstract:The use of organic photodiodes (OPDs) for measuring phosphorescent lifeTimes of optochemical oxygen sensors is described. Phosphorescent indicators with lifeTimes ranging from ∼5 to 60 μs have been studied using light-emitting diodes as the excitation source and organic photodiodes integrated into the sensor substrate for detection. A measurement system using an adjusted electronic circuitry to detect photocurrents in the nanoampere range is presented. The response behaviour of the organic photodiodes has been characterized, and it was found that a forward (positive) bias had to be applied in order to decrease the response Time of the OPDs to a range suitable for phosphorescence Decay Time measurements. A modulation cutoff frequency of ∼100 kHz has been determined, corresponding to a response Time of the organic photodiodes of 1.6 μs. Two sensor dyes have been characterized regarding their lifeTimes upon exposure to 0–20 % oxygen, and it was shown that results comparable to literature data and inorganic photodetectors can be achieved.
Saso Mladenovski - One of the best experts on this subject based on the ideXlab platform.
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detailed analysis of exciton Decay Time change in organic light emitting devices caused by optical effects
Journal of The Society for Information Display, 2011Co-Authors: Saso Mladenovski, Sebastian Reineke, Lieven Penninck, Kristiaan NeytsAbstract:— The exciton Decay Time in organic light-emitting devices (OLEDs) depends on the optical environment, i.e., the thicknesses and refractive indices of all layers in a device. The Decay of an exciton can occur through a radiative or a non-radiative channel. Each of these channels has a probability, which is expressed by, respectively, the radiative and the non-radiative Decay rate. The radiative Decay rate is influenced by the optical environment, i.e., the OLED's thin-film layer structure. In this paper, a model for estimating the change of the exciton Decay Time (inverse of the Decay rate) is presented. In addition, the Decay Time change in both top- and bottom-emitting OLEDs as a function of the charge-transport layer thicknesses has been investigated. Furthermore, the most important mechanism responsible for the exciton Decay Time change is outlined.
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measurement and simulation of exciton Decay Times in organic light emitting devices with different layer structures
Optics Letters, 2009Co-Authors: Saso Mladenovski, Sebastian Reineke, Kristiaan NeytsAbstract:The Decay Time of an exciton depends on the coupling between the dipole oscillator and the optical environment in which it is placed. For an organic light-emitting device this environment is determined by the thin-film layer structure. The radiative Decay competes with nonradiative Decay channels and in this way influences the luminescent efficiency and the external quantum efficiency of the device. We describe a method to estimate the dependency of the exciton Decay Time and the luminescent efficiency on the thin-film stack and validate the results experimentally.
