Reliability Study of a Fluorescent Blue Organic Light-Emitting Device

2006 ◽  
Vol 965 ◽  
Author(s):  
Jiun-Haw Lee ◽  
Yu-Hsuan Ho ◽  
Tien-Chun Lin ◽  
Chia-Fang Wu
Keyword(s):  
High Efficiency ◽  
Hole Transport ◽  
Transport Layer ◽  
Constant Current ◽  
Electron Transport Layer ◽  
Hole Transport Layer ◽  
High Electron ◽  
Device Structure ◽  
Light Emitting ◽  
Order Of Magnitude

ABSTRACTIn this paper, we measured and analyzed the operation lifetime of a high efficiency blue OLED which consists of N,N' –Vdiphenyl -N,N'-bis(1-napthyl) -1,1'-biphenyl-4,4'- diamine (NPB) as the hole-transport layer (HTL), 4,4'-bis[2-(4-(N,N-diphenylamino)phenyl)vinyl]biphenyl (DPAVBi) doped in 9,10-bis(2';-naphthyl) anthracene (ADN) as the emitting layer (EML), and bis(10-hydroxyben-zo[h]quinolinato)beryllium (Bebq2) as the electron-transport layer (ETL). Due to the high electron mobility of the ETL (one order of magnitude higher than Alq3), the carrier balance is achieved and a blue OLED with a high external quantum efficiency of 8.32% is obtained. The device structure of our blue OLED device is ITO /HTL (40nm)/EML (45nm, 4% dopant)/ETL (15nm)/ LiF(1.2nm)/Al (100nm). In our operation lifetime measurement, we fixed the initial luminescence of the blue OLEDs at 12500, 10000, 7000, 5000 cd/m2 with a constant current driving. The resulting half-lifetime are 5.58, 16.56, 27, 109.819 hours, respectively. To estimate the half-lifetime of this device, we use a well-known relation in our fitting: L*t1/2n= constant where n is the acceleration coefficient, and t1/2 is the half-lifetime. In our blue OLED, the n value is 3.088. By using the equation, we can calculate that the estimated half lifetime at an initial luminance of 1000 cd/m2 achieves 15611 hours in our device. For further investigating the lifetime mechanism in our blue OLED, we fit all the luminance versus time curves obtained under different driving condition. We found that luminance is inversely proportional to the square of the time, rather than a typically stretched exponential decay which means the luminance decay is a second-order reaction in our blue OLED.

Investigation of a Novel Light-blue-emitting Fluorescent Guest/Host System with Excellent Lifetime

2006 ◽  
Vol 916 ◽  
Author(s):  
Philipp van Gemmern ◽  
Stefan P. Grabowski ◽  
Herbert Boerner ◽  
Volker van Elsbergen ◽  
Hans-Peter Löbl ◽  
...  
Keyword(s):  
Hole Transport ◽  
Transport Layer ◽  
Constant Current ◽  
Electron Transport Layer ◽  
Hole Transport Layer ◽  
Charge Balance ◽  
Light Emitting ◽  
Host System ◽  
Light Emitting Devices ◽  
Organic Light

AbstractIn this work, organic light emitting devices (OLEDs) based on a blue-emitting fluorescent guest/host-system from Merck OLED Materials GmbH is investigated. OLEDs comprising a hole transport layer (HTL), the emissive film Merck Blue Host:Merck Blue Guest (MBH:MBG), a hole-blocking film and the electron transport layer (ETL) were prepared by vacuum thermal evaporation. The hole-blocking capabilities of aluminum(III)bis(2-methyl-8-quinolinato)4-phenylphenolate (BAlq) and the host material MBH were investigated. By employing an additional HBL, the current efficiency could be increased from 5.7 to 7.4 cd/A. Furthermore, 2,3,5,6-tetrafluoro-7,7,8,8-tetracyano-quinodimethane (F4-TCNQ) doping of the HTL was investigated. Devices with 4,7-diphenyl-1,10-phenanthroline (BPhen) or 1,3,5-Tris-(N-phenylbenzimidazol-2-yl)benzene (TPBI) as alternative ETLs were fabricated and conclusions were drawn regarding the charge balance in the devices. It was found that employing tris-(8-hydroxyquinoline) aluminum (Alq3) as ETL leads to the best lifetimes of about 2000 hours at a constant current of 20 mA/cm2 while p-doping in combination with BPhen as ETL leads to the highest efficiency of 5.7 lm/W max. and 4.4 lm/W at 1000 cd/m2.

scholarly journals Improvement of Quantum Dot Light Emitting Device Characteristics by CdSe/ZnS Blended with HMDS (Hexamethyldisilazane)

2020 ◽  
Vol 10 (17) ◽  
pp. 6081
Author(s):  
Junekyun Park ◽  
Eunkyu Shin ◽  
Jongwoo Park ◽  
Yonghan Roh
Keyword(s):  
Quantum Dot ◽  
Photoelectron Spectroscopy ◽  
Surface Defects ◽  
Hole Transport ◽  
Transport Layer ◽  
Electron Transport Layer ◽  
Hole Transport Layer ◽  
Atmospheric Conditions ◽  
Light Emitting ◽  
X Ray

We demonstrated the way to improve the characteristics of quantum dot light emitting diodes (QD-LEDs) by adding a simple step to the conventional fabrication process. For instance, we can effectively deactivate the surface defects of quantum dot (QD) (e.g., CdSe/ZnS core-shell QDs in the current work) with the SiO bonds by simply mixing QDs with hexamethyldisilazane (HMDS) under atmospheric conditions. We observed the substantial improvement of device characteristics such that the current efficiency, the maximum luminance, and the QD lifetime were improved by 1.7–1.8 times, 15–18%, and nine times, respectively, by employing this process. Based on the experimental data (e.g., energy dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS)), we estimated that the growth of the SiOx on the surface of QDs is self-limited: the SiOx are effective to passivate the surface defects of QDs without deteriorating the intrinsic properties including the color-purity of QDs. Second, we proposed that the emission profiling study can lead us to the fundamental understanding of charge flow in each layer of QD-LEDs. Interestingly enough, many problems related to the charge-imbalance phenomenon were simply solved by selecting the combination of thicknesses of the hole transport layer (HTL) and the electron transport layer (ETL).

High luminance of CuInS2-based yellow quantum dot light emitting diodes fabricated by all-solution processing

RSC Advances ◽  
2016 ◽  
Vol 6 (76) ◽  
pp. 72462-72470 ◽  
Author(s):  
Jingling Li ◽  
Hu Jin ◽  
Kelai Wang ◽  
Dehui Xie ◽  
Dehua Xu ◽  
...  
Keyword(s):  
Electron Transport ◽  
Quantum Dot ◽  
Zno Nanoparticles ◽  
Light Emitting Diodes ◽  
Hole Transport ◽  
Transport Layer ◽  
Electron Transport Layer ◽  
Hole Transport Layer ◽  
High Luminance ◽  
Light Emitting

In this work, all-solution processed, multi-layer yellow QLEDs, consisting of a hole transport layer of poly(9-vinylcarbazole), emissive layer of ligand exchanged CuInS2/ZnS QDs, and electron transport layer of ZnO nanoparticles, are fabricated.

Degradation of Bilayer Organic Light-Emitting Diodes Studied by Impedance Spectroscopy

2016 ◽  
Vol 16 (4) ◽  
pp. 3368-3372 ◽  
Author(s):  
Shuri Sato ◽  
Masashi Takata ◽  
Makoto Takada ◽  
Hiroyoshi Naito
Keyword(s):  
Impedance Spectroscopy ◽  
Light Emitting Diodes ◽  
Device Simulation ◽  
Hole Transport ◽  
Organic Light Emitting Diodes ◽  
Transport Layer ◽  
Electron Transport Layer ◽  
Hole Transport Layer ◽  
Light Emitting ◽  
Organic Light

The degradation of bilayer organic light-emitting diodes (OLEDs) with a device structure of N, N′-di(1-naphthyl)-N, N′-diphenylbenzidine (α-NPD) (hole transport layer) and tris-(8-hydroxyquinolate)aluminum (Alq3) (emissive layer and electron transport layer) has been studied by impedance spectroscopy and device simulation. Two modulus peaks are found in the modulus spectra of the OLEDs below the electroluminescence threshold. After aging of the OLEDs, the intensity of electroluminescence is degraded and the modulus peak due to the Alq3 layer is shifted to lower frequency, indicating that the resistance of the Alq3 layer is increased. Device simulation reveals that the increase in the resistance of the Alq3 layer is due to the decrease in the electron mobility in the Alq3 layer.

Highly-Efficient Solution-Processed Organic Light Emitting Diodes with Blend V2O5-PEDOT:PSS Hole-Injection/Hole-Transport Layer

MRS Advances ◽  
2019 ◽  
Vol 4 (31-32) ◽  
pp. 1779-1786 ◽  
Author(s):  
Rohit Ashok Kumar Yadav ◽  
Mangey Ram Nagar ◽  
Deepak Kumar Dubey ◽  
Sujith Sudheendran Swayamprabha ◽  
Jwo-Huei Jou
Keyword(s):  
Power Efficiency ◽  
High Efficiency ◽  
Hole Transport ◽  
Organic Light Emitting Diodes ◽  
Transport Layer ◽  
Hole Injection ◽  
Hole Transport Layer ◽  
Injection Hole ◽  
Light Emitting ◽  
Organic Light

ABSTRACTOrganic light-emitting diodes (OLEDs) have attracted huge concern because of their intrinsic characteristics and ability to reach the pinnacle in the field of high-quality flat-panel displays and energy-efficient solid-state lighting. High-efficiency is always a key crux for OLED devices being energy-saving and longer life-span. OLEDs have encountered enormous difficulties in meeting the requirements for large-sized devices due to a major limitation in vacuum thermal evaporation technology. In multilayered OLED devices, the characteristics of the charge injection/transport layer is a crucial factor for the operating-voltage, power-efficiency and stability of the device. Transition metal oxides have shown great potential owing to their wide range of possible energy level alignments, balanced charge injection, and improvement of carrier mobilities. In this study, we report a solution-processed blend V2O5-PEDOT:PSS hole-injection/hole-transport layer (HIL/HTL) for efficient orange phosphorescent OLEDs. The electroluminescent characteristics of blend V2O5-PEDOT:PSS based devices were studied with the structure ITO/V2O5-PEDOT:PSS/CBP:Ir(2-phq)3/TPBi/LiF/Al. The V2O5-PEDOT:PSS based OLEDs displayed relatively higher device performance and low roll-off than that of the counter PEDOT:PSS device in terms of a maximum luminance of 17,670 cd m-2, power efficiency of 19.4 lm W-1, external quantum efficiency of 8.7%, and more importantly, low turn-on voltage. These results demonstrate an alternative approach based on metal oxide/organic blend HIL/HTL as a substitute of PEDOT:PSS for high-efficiency solution process OLEDs.

scholarly journals Highly Stable Inverted CdSe/ZnS-Based Light-Emitting Diodes by Nonvacuum Technique ZTO as the Electron-Transport Layer

Electronics ◽  
2021 ◽  
Vol 10 (18) ◽  
pp. 2290
Author(s):  
Sajid Hussain ◽  
Fawad Saeed ◽  
Ahmad Raza ◽  
Abida Parveen ◽  
Ali Asghar ◽  
...  
Keyword(s):  
Electron Transport ◽  
High Efficiency ◽  
Light Emitting Diodes ◽  
Minimum Energy ◽  
High Mobility ◽  
Transport Layer ◽  
Electron Transport Layer ◽  
Device Structure ◽  
Light Emitting ◽  
Device Efficiency

CdSe/ZnS quantum dots (QDs) have attracted great consideration from investigators owing to their excellent photo-physical characteristics and application in quantum dot light-emitting diodes (QD-LEDs). The CdSe/ZnS-based inverted QD-LEDs structure uses high-quality semiconductors electron transport layers (ETLs), a multilayered hole transporting layers (HTLs). In QD-LED, designing a device structure with a minimum energy barrier between adjacent layers is very important to achieve high efficiency. A high mobility polymer of poly (9,9-dioctylfluorene-co-N-(4-(3-methylpropyl)) diphenylamine (TFB) was doped with 4,4′-bis-(carbazole-9-yl) biphenyl (CBP) with deep energy level to produce composite TFB:CBP holes to solve energy mismatch (HTL). In addition, we also improved the QD-LED device structure by using zinc tin oxide (ZTO) as ETL to improve device efficiency. The device turn-on voltage Vt (1 cd m−2) with ZTO ETL reduced from 2.4 V to 1.9 V significantly. Furthermore, invert structure devices exhibit luminance of 4296 cd m−2, current-efficiency (CE) of 7.36 cd A−1, and external-quantum efficiency (EQE) of 3.97%. For the QD-LED based on ZTO, the device efficiency is improved by 1.7 times.

Long-Term Degradation Mechanism of Organic Light Emitting Devices Based on Small Molecules

1999 ◽  
Vol 558 ◽  
Author(s):  
Hany Aziz ◽  
Zoran D. Popovic ◽  
Nan-Xing Hu ◽  
Ah-Mee Hor ◽  
Gu Xu
Keyword(s):  
Degradation Mechanism ◽  
Hole Transport ◽  
Transport Layer ◽  
Constant Current ◽  
Hole Transport Layer ◽  
Light Emitting ◽  
Light Emitting Devices ◽  
Organic Light ◽  
Organic Light Emitting Devices

ABSTRACTThe intrinsic degradation of tris(8-hydroxyquinoline) aluminum (AlQ3)-based organic light emitting devices, that leads to the long-term decrease in the electroluminescence efficiency of the devices operated under constant current conditions, is studied. The injection of holes in A1Q3 is found to be the main factor responsible for device degradation. OLEDs with dual HTLs in different arrangements are also presented to demonstrate the proposed degradation mechanism. The role of various approaches to increase OLED lifetime, such as, doping the hole transport layer, introducing a buffer layer at the hole-injecting contact, or using a mixed emitting layer of hole and electron transporting molecules, is explained.

scholarly journals Synergy of Bis(Sulfanylidene)Tungsten and Spiro-Ometad for an Efficient Perovskite Solar Cell

2019 ◽  
Vol 9 (1) ◽  
pp. 4011-4016
Keyword(s):  
Solar Cells ◽  
Solar Cell ◽  
High Efficiency ◽  
Perovskite Solar Cells ◽  
Perovskite Solar Cell ◽  
Hole Transport ◽  
Transport Layer ◽  
Electron Transport Layer ◽  
Hole Transport Layer ◽  
Direct Band

The researchers now days are avid of solar cells despite the efficiency issues. As lead-based halide perovskite exhibit toxic nature alternatives for the anti- toxic perovskite solar cells(PSCs) are gaining much research. Bis(sulfanylidene )tungsten is a toxic free feasible emerging option with direct band gap of value 1.8 eV. Tungsten disulfide is other chemical name of Bis(sulfanylidene)tungsten. In this paper, perovskite solar cell (PSC) with Bis(sulfanylidene)tungsten (WS2 ) as electron transport layer and spiro-OMeTAD as hole transport layer is modelled and simulated using SCAPS software to analyze performance parameters. The device simulations results are compared for comprehensive defect study of WS2 as ETL. With integration of WS2 and spiro-OMeTAD in the perovskite design, the outcomes are proficient enough with 25.96% of PCE, 22.06 mA/cm2 Jsc, 1.280V Voc and 91.76% FF. Launching the batch setup for absorber layer thickness further resulted with competent PCE 27.78%. The outcomes signified that the toxic-free WS2 based PSC can be a prominent upcoming perspective in terms of environmentally pristine nature and capitulate comparative high efficiency

scholarly journals Design and simulation of a high-performance Cd-free Cu2SnSe3 solar cells with SnS electron-blocking hole transport layer and TiO2 electron transport layer by SCAPS-1D

2021 ◽  
Vol 3 (2) ◽  
Author(s):  
M. Atowar Rahman
Keyword(s):  
Solar Cells ◽  
Electron Transport ◽  
Carrier Concentration ◽  
High Efficiency ◽  
Hole Transport ◽  
Absorber Layer ◽  
Cell Performance ◽  
Transport Layer ◽  
Electron Transport Layer ◽  
Hole Transport Layer

AbstractThis article presents numerical investigations of the novel (Ni/SnS/Cu2SnSe3/TiO2/ITO/Al) heterostructure of Cu2SnSe3 based solar cell using SCAPS-1D simulator. Purpose of this research is to explore the influence of SnS hole transport layer (HTL) and TiO2 electron transport layer (ETL) on the performance of the proposed cell. Based on the proposed device architecture, effects of thickness and carrier concentration of absorber layer, SnS HTL, TiO2 ETL, absorber layer defect density, operating temperature and back-contact metal work function (BMWF) are studied to improve the cell performance. Our initial simulation results show that if SnS HTL is not introduced, the efficiency of standard Cu2SnSe3 cell is 1.66%, which is well agreed with the reported experimental results in literature. However, by using SnS and TiO2 as HTL and ETL, respectively and optimizing the cell parameters, a simulated efficiency of up to 27% can be achieved. For Cu2SnSe3 absorber layer, 5 × 1017 cm−3 and 1500 nm are the optimal values of carrier concentration and thickness, respectively. On the other hand, the BMWF is estimated to be greater than 5.2 eV for optimum cell performance. Results of this contribution can provide constructive research avenues for thin-films photovoltaic industry to fabricate cost-effective, high-efficiency and cadmium-free Cu2SnSe3-based solar cells.

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