scholarly journals Temporal Response of MSM-LED Optical Integrated Device

2011 ◽  
Vol 2011 ◽  
pp. 1-4
Author(s):  
Sh. M. Eladl ◽  
M. A. Ashour
Keyword(s):  
Frequency Response ◽  
Optical Feedback ◽  
Light Emitting Diode ◽  
Cutoff Frequency ◽  
Temporal Response ◽  
Device Structure ◽  
Light Emitting ◽  
Msm Photodetector ◽  
Response Output ◽  
Integrated Device

The temporal response of an optical integrated device is theoretically analysed. The device is composed of a Metal-Semiconductor-Metal (MSM) Photodetector and a Light Emitting Diode (LED). The analysis is based on the frequency response of the constituent devices without any optical feedback within the device structure. All expressions describing the frequency response, time response, output derivatives, and rise time are outlined. The results show that the temporal response of MSM detectors is similar to the LED response if the cutoff frequency of the LED is lower than that of MSM, while it is similar to MSM detector if the cutoff frequency of the MSM is lower than that of LED.

Synchronization of Chaotic Quantum Dot Light Emitting Diodes under Optical Feedback Effect

2020 ◽  
pp. 144-148
Keyword(s):  
Quantum Dot ◽  
Delay Time ◽  
Chaos Synchronization ◽  
Optical Feedback ◽  
Light Emitting Diode ◽  
Feedback Effect ◽  
Complete Synchronization ◽  
Light Emitting ◽  
Coupling Methods ◽  
Coupling Parameters

Chaos synchronization of delayed quantum dot light emitting diode has been studied theortetically which are coupled via the unidirectional and bidirectional. at synchronization of chaotic, The dynamics is identical with delayed optical feedback for those coupling methods. Depending on the coupling parameters and delay time the system exhibits complete synchronization, . Under proper conditions, the receiver quantum dot light emitting diode can be satisfactorily synchronized with the transmitter quantum dot light emitting diode due to the optical feedback effect.

scholarly journals Silicon Quantum Dot Light Emitting Diode at 620 nm

Micromachines ◽  
2019 ◽  
Vol 10 (5) ◽  
pp. 318 ◽  
Author(s):  
Hiroyuki Yamada ◽  
Naoto Shirahata
Keyword(s):  
Quantum Dot ◽  
High Performance ◽  
Light Emitting Diode ◽  
Optically Active ◽  
Driving Voltage ◽  
Device Structure ◽  
Light Emitting ◽  
Naked Eye ◽  
Turn On ◽  
Silicon Quantum Dot

Here we report a quantum dot light emitting diode (QLED), in which a layer of colloidal silicon quantum dots (SiQDs) works as the optically active component, exhibiting a strong electroluminescence (EL) spectrum peaking at 620 nm. We could not see any fluctuation of the EL spectral peak, even in air, when the operation voltage varied in the range from 4 to 5 V because of the possible advantage of the inverted device structure. The pale-orange EL spectrum was as narrow as 95 nm. Interestingly, the EL spectrum was narrower than the corresponding photoluminescence (PL) spectrum. The EL emission was strong enough to be seen by the naked eye. The currently obtained brightness (∼4200 cd/m2), the 0.033% external quantum efficiency (EQE), and a turn-on voltage as low as 2.8 V show a sufficiently high performance when compared to other orange-light-emitting Si-QLEDs in the literature. We also observed a parasitic emission from the neighboring compositional layer (i.e., the zinc oxide layer), and its intensity increased with the driving voltage of the device.

Filtered Optical Feedback in Quantum Dot Light Emitting Diode

2018 ◽  
Vol 915 ◽  
pp. 171-178 ◽  
Author(s):  
Kais A.M. Al Naimee ◽  
Hussein B. Al Husseini ◽  
Amin H. Al Khursan ◽  
Sora F. Abdalah ◽  
Riccardo Meucci ◽  
...  
Keyword(s):  
Quantum Dot ◽  
Optical Feedback ◽  
Chaotic Behavior ◽  
Light Emitting Diode ◽  
Unexpected Result ◽  
Light Emitting ◽  
Mixed Mode Oscillations ◽  
Filter Width ◽  
Point Analysis ◽  
First Time

This research reports a theoretical investigation on the role of filtered optical feedback (FOF) in the quantum dot light emitting diode (QD-LED). The underlying dynamics is affected by a sidle node, which returns to an elliptical shape when the wetting layer (WL) is neglected. Both filter width and time delay change the appearance of different dynamics (chaotic and mixed mode oscillations ,MMOs). The results agrees with the experimental observations. Here, the fixed point analysis for QDs was done for the first time. For QD-LED with FOF, the system transits from the coherence collapse (CC) case in conventional optical feedback (COF) to a coherent case with a filtered mode in FOF. It was found that the WL washes out the modes which is an unexpected result. This may attributed to the longer capture time of WL compared with that between QD states. Thus, WL reduces the chaotic behavior.

Investigation of 4,4′- bis [(N carbazole) styryl] biphenyl (BSB4) for a pure blue fluorescent OLED with enhanced efficiency nearing the theoretical limit

2022 ◽  
Author(s):  
Dhruvajyoti Barah ◽  
Subhamoy Sahoo ◽  
Naga Sai Manoj Inaganti ◽  
Haripriya Kesavan ◽  
Jayeeta Bhattacharyya ◽  
...  
Keyword(s):  
Light Emitting Diode ◽  
Blue Emission ◽  
Blue Shift ◽  
Optical Simulation ◽  
Charge Balance ◽  
Theoretical Limit ◽  
Optical Interference ◽  
Device Structure ◽  
Light Emitting ◽  
Emissive Layer

Abstract 4,4′-bis[(N-carbazole) styryl] biphenyl (BSB4 or BSBCz) is one of the widely studied organic fluorescent materials for blue organic electroluminescent devices in the recent times. In this work, BSB4 is used as a guest material to construct the host-guest matrix for the emissive layer (EML) of a pure blue fluorescent organic light-emitting diode (OLED). A pure blue emission suitable for display application with a Commission Internationale de l’Eclairage (CIE) coordinate of (0.147, 0.070) is achieved by the blue-shift of the emission spectrum of the host-guest matrix from that of the pristine guest (BSB4) molecules. The optimization of OLED structures is carried out by considering (i) charge balance in the emissive layer for high exciton density, and (ii) optical interference of generated light in the organic layers for increased light outcoupling. A thorough comparative study on the use of different combinations of widely used hole and electron transport layers to obtain charge balance in the EML of the OLED, thereby enhancing the external quantum efficiency (EQE) is shown. Optical interference effects in the fabricated OLEDs are analyzed by optical simulation of each device structure by transfer matrix method (TMM). With the optimized device structures, we are able to overcome the 2% EQE limit that has been reported so far for blue fluorescent OLEDs with BSB4 as light emitting material and achieve a maximum EQE of 4.08%, which is near to the theoretical limit of EQE for fluorescent OLEDs.

A hybrid white organic light-emitting diode with above 20% external quantum efficiency and extremely low efficiency roll-off

2014 ◽  
Vol 2 (36) ◽  
pp. 7494-7504 ◽  
Author(s):  
Ning Sun ◽  
Qi Wang ◽  
Yongbiao Zhao ◽  
Dezhi Yang ◽  
Fangchao Zhao ◽  
...  
Keyword(s):  
Quantum Efficiency ◽  
External Quantum Efficiency ◽  
Light Emitting Diode ◽  
Structure Design ◽  
Device Structure ◽  
Light Emitting ◽  
Organic Light Emitting Diode ◽  
Organic Light ◽  
Low Efficiency

Based on a delicate device structure design, a novel (phosphorescence/fluorescence) hybrid WOLED with nearly 100% exciton harvesting has been demonstrated.

scholarly journals Highly Efficient White Organic Light-Emitting Diodes with Controllable Excitons Behavior by a Mixed Interlayer between Fluorescence Blue and Phosphorescence Yellow-Emitting Layers

2013 ◽  
Vol 2013 ◽  
pp. 1-7 ◽  
Author(s):  
Chun-Hong Gao ◽  
Xiao-Bo Shi ◽  
Dong-Ying Zhou ◽  
Lei Zhang ◽  
Zhao-Kui Wang ◽  
...  
Keyword(s):  
Power Efficiency ◽  
Carrier Transport ◽  
Layer Structure ◽  
Light Emitting Diode ◽  
Device Structure ◽  
Emission Layer ◽  
Light Emitting ◽  
Organic Light Emitting Diode ◽  
Highly Efficient ◽  
Organic Light

A highly efficient hybrid white organic light-emitting diode (HWOLED) has been demonstrated with a mixed interlayer between fluorescent blue and phosphorescent yellow-emitting layers. The device structure is simplified by using a controllable fluorescence-mixed interlayer-phosphorescence emission layer structure. The electroluminance (EL) performance can be modulated easily by adjusting the ratio of the hole-predominated material to the electron-predominated material in the interlayer. It is found that the HWOLED with a ratio of 3 : 2 exhibits a current efficiency of 34 cd/A and a power efficiency of 29 lm/W at 1000 cd/m2with warm white Commission Internationale de l’Eclairage (CIE1931) coordinates of (0.4273, 0.4439). The improved efficiency and adaptive CIE coordinates are attributed to the controllable mixed interlayer with enhanced charge carrier transport, optimized excitons distribution, and improved harvestings of singlet and triplet excitons.

External modes in quantum dot light emitting diode with filtered optical feedback

2016 ◽  
Vol 119 (22) ◽  
pp. 224301 ◽  
Author(s):  
Hussein B. Al Husseini ◽  
Kais A. Al Naimee ◽  
Amin H. Al-Khursan ◽  
Ali. H. Khedir
Keyword(s):  
Quantum Dot ◽  
Optical Feedback ◽  
Light Emitting Diode ◽  
Light Emitting

Effect of thermal annealing on the performance of polysilane based organic light emitting diode

2008 ◽  
Vol 1091 ◽  
Author(s):  
Ranbir Singh ◽  
Monica Katiyar
Keyword(s):  
Thermal Annealing ◽  
Indium Tin Oxide ◽  
Light Emitting Diode ◽  
Peak Current Density ◽  
Device Structure ◽  
Light Emitting ◽  
White Emission ◽  
Near Ultraviolet ◽  
Organic Light ◽  
Interchain Interactions

AbstractPolysilanes, being ó bonded, are promising materials for emission in ultraviolet/near ultraviolet (UV/NUV) region and exhibit adequate charge mobility for fabricating practical devices. This study contributes to the understanding of the effects of thermal annealing on the performance of organic light-emitting diodes (OLEDs) made of poly (n-butylphenyl-silane) (PS-4). OLEDs having indium tin oxide (ITO)/poly (3, 4-ethylenedioxythiophene) poly (styrenesulfonate) PEDOT: PSS/poly (n-butylphenylsilane) (PS-4)/lithium fluoride (LiF)/Al device structure were fabricated. PS-4 is spin coated and annealed for one hour at different temperatures (90-120°C). EL Spectra from these devices consists of white emission along with the UV peak. Current density-voltage (J-V), photoluminescence (PL) and electroluminescence (EL) spectra are also measured. White emission is significantly suppressed when PS-4 is annealed at higher temperature and threshold voltage is lowest at 110°C annealing temperature. This is correlated with PL emission and structural properties of PS-4 films. Surface morphology of PS-4 was measured using atomic force microscopy (AFM). The results are explained in terms of effect of annealing of polymer films on interchain interactions.

scholarly journals New Electroactive Polymers with Electronically Isolated 4,7-Diarylfluorene Chromophores as Positive Charge Transporting Layer Materials for OLEDs

Molecules ◽  
2021 ◽  
Vol 26 (7) ◽  
pp. 1936
Author(s):  
Gintare Krucaite ◽  
Daiva Tavgeniene ◽  
Dovydas Blazevicius ◽  
Baohua Zhang ◽  
Aivars Vembris ◽  
...  
Keyword(s):  
Light Emitting Diode ◽  
Polymeric Materials ◽  
Thin Layers ◽  
Device Structure ◽  
Light Emitting ◽  
Full Characterization ◽  
Organic Light ◽  
Electron Transporting Layer ◽  
Hole Transporting ◽  
Electron Photoemission

A group of polyethers containing electroactive pendent 4,7-diarylfluorene chromophores have been prepared by the multi-step synthetic route. Full characterization of their structures has been presented. The polymeric materials represent derivatives of high thermal stability with initial thermal degradation temperatures in a range of 392–397 °C. Glass transition temperatures of the amorphous polymers range from 28 °C to 63 °C and depend on structures of the 4,7-diarylfluorene chromophores. Electron photoemission spectra of thin layers of the electroactive derivatives showed ionization potentials in the range of 5.8–6.0 eV. Hole injecting/transporting properties of the prepared polymeric materials were confirmed during formation of organic light-emitting diodes with tris(quinolin-8-olato)aluminium (Alq3) as a green emitter, which also serves as an electron transporting layer. The device using hole-transporting polymer with electronically isolated 2,7-di(4-biphenyl)fluorene chromophores demonstrated the best overall performance with low turn on voltage of 3 V, high current efficiency exceeding 1.7 cd/A, and with maximum brightness over 200 cd/m2. The organic light-emitting diode (OLED) characteristics were measured in non-optimized test devices. The efficiencies could be further improved by an optimization of device structure, formation conditions, and encapsulation of the devices.

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