Improved performance of organic light-emitting diodes with MoO3 interlayer by oblique angle deposition

Cataloged from PDF version of article.We fabricated and demonstrated improved organic light emitting diodes (OLEDs) in a thin film architecture of indium tin oxide (ITO)/molybdenum trioxide (MoO3) (20 nm)/ N,N'-Di(naphth-2-yl)-N,N'-diphenyl-benzidine (NPB) (50 nm)/tris-(8-hydroxyquinoline) (Alq(3)) (70 nm)/Mg:Ag (200 nm) using an oblique angle deposition technique by which MoO3 was deposited at oblique angles (theta) with respect to the surface normal. It was found that, without sacrificing the power efficiency of the device, the device current efficiency and external quantum efficiency were significantly enhanced at an oblique deposition angle of theta = 60 degrees for MoO3. (C) 2011 Optical Society of Americ

On the triplet distribution and its effect on an improved phosphorescent organic light-emitting diode

Cataloged from PDF version of article.We reported phosphorescent organic light-emitting diodes with internal quantum efficiency near 100% with significantly reduced efficiency roll-off. It was found that the use of different hole transporting layer (HTL) affects the exciton distribution in the emission region significantly. Our best device reaches external quantum efficiency (EQE), current, and power efficiency of 22.8% +/- 0.1%, 78.6 +/- 0.2 cd/A, 85 +/- 2 lm/W, respectively, with half current of 158.2 mA/cm(2). This considerably outperforms the control device with N,N'-bis(naphthalen-1-yl)-N,N'-bis(phenyl)-benzidine (NPB) (HTL) and 4,4'-N,N'-dicarbazole-biphenyl (host) with maximum EQE, current and power efficiency of 19.1% +/- 0.1%, 65.6 +/- 0.3 cd/A, 67 +/- 2 lm/W, respectively, with half current of only 8.1 mA/cm(2). (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4749278

An efficient non-Lambertian organic light-emitting diode using imprinted submicron-size zinc oxide pillar arrays

Cataloged from PDF version of article.We report phosphorescent organic light-emitting diodes with a substantially improved light outcoupling efficiency and a wider angular distribution through applying a layer of zinc oxide periodic nanopillar arrays by pattern replication in non-wetting templates technique. The devices exhibited the peak emission intensity at an emission angle of 40 degrees compared to 0 degrees for reference device using bare ITO-glass. The best device showed a peak luminance efficiency of 95.5 +/- 1.5 cd/ A at 0 degrees emission (external quantum efficiency-EQE of 38.5 +/- 0.1%, power efficiency of 127 +/- 1lm/W), compared to that of the reference device, which has a peak luminance efficiency of 68.0 +/- 1.4 cd/ A (EQE of 22.0 +/- 0.1%, power efficiency of 7261 lm/W). (C) 2013 American Institute of Physics

A bright cadmium-free, hybrid organic/quantum dot white light-emitting diode

Cataloged from PDF version of article.We report a bright cadmium-free, InP-based quantum dot light-emitting diode (QD-LED) with efficient green emission. A maximum brightness close to 700 cd/m(2) together with a relatively low turn-on voltage of 4.5 V has been achieved. With the design of a loosely packed QD layer resulting in the direct contact of poly[N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)benzidine] (poly-TPD) and 2,2',2 ''-(1,3,5-benzinetriyl)-tris(1-phenyl-1-H-benzimidazole) (TPBi) in the device, a ternary complementary white QD-LED consisting of blue component (poly-TPD), green component (QDs), and red component (exciplex formed at the interface between poly-TPD and TPBi) has been demonstrated. The resulting white QD-LED shows an excellent color rendering index of 95. (C) 2012 American Institute of Physics

Transition metal oxides on organic semiconductors

Cataloged from PDF version of article.Transition metal oxides (TMOs) on organic semiconductors (OSs) structure has been widely used in inverted organic optoelectronic devices, including inverted organic light-emitting diodes (OLEDs) and inverted organic solar cells (OSCs), which can improve the stability of such devices as a result of improved protection of air sensitive cathode. However, most of these reports are focused on the anode modification effect of TMO and the nature of TMO-on-OS is not fully understood. Here we show that the OS on TMO forms a two-layer structure, where the interface mixing is minimized, while for TMO-on-OS, due to the obvious diffusion of TMO into the OS, a doping-layer structure is formed. This is evidenced by a series of optical and electrical studies. By studying the TMO diffusion depth in different OS, we found that this process is governed by the thermal property of the OS. The TMO tends to diffuse deeper into the OS with a lower evaporation temperature. It is shown that the TMO can diffuse more than 20 nm into the OS, depending on the thermal property of the OS. We also show that the TMO-on-OS structure can replace the commonly used OS with TMO doping structure, which is a big step toward in simplifying the fabrication process of the organic optoelectronic devices. (C) 2014 Elsevier B.V. All rights reserved

Quantum Dot Light-Emitting Diode with Quantum Dots Inside the Hole Transporting Layers

Cataloged from PDF version of article.We report a hybrid, quantum dot (QD)-based, organic light-emitting diode architecture using a noninverted structure with the QDs sandwiched between hole transporting layers (HTLs) outperforming the reference device structure implemented in conventional noninverted architecture by over five folds and suppressing the blue emission that is otherwise observed in the conventional structure because of the excess electrons leaking towards the HTL. It is predicted in the new device structure that 97.44% of the exciton formation takes place in the QD layer, while 2.56% of the excitons form in the HTL. It is found that the enhancement in the external quantum efficiency is mainly due to the stronger confinement of exciton formation to the QDs

An efficient non-Lambertian organic light-emitting diode using imprinted submicron-size zinc oxide pillar arrays

We report phosphorescent organic light-emitting diodes with a substantially improved light outcoupling efficiency and a wider angular distribution through applying a layer of zinc oxide periodic nanopillar arrays by pattern replication in non-wetting templates technique. The devices exhibited the peak emission intensity at an emission angle of 40° compared to 0° for reference device using bare ITO-glass. The best device showed a peak luminance efficiency of 95.5 ± 1.5 cd/A at 0° emission (external quantum efficiency - EQE of 38.5 ± 0.1%, power efficiency of 127 ± 1 lm/W), compared to that of the reference device, which has a peak luminance efficiency of 68.0 ± 1.4 cd/A (EQE of 22.0 ± 0.1%, power efficiency of 72 ± 1 lm/W). © 2013 American Institute of Physics

AC-driven, color- and brightness-tunable organic light-emitting diodes constructed from an electron only device

In this paper, a color- and brightness-tunable organic light-emitting diode (OLED) is reported. This OLED was realized by inserting a charge generation layer into an electron only device to form an n-i-p-i-n structure. It is shown that, by changing the polarity of applied voltage, only the p-i-n junction operated under positive bias can emit light and, by applying an AC voltage, emission from both junctions was realized. It is also shown that, by using a combination of blue- and red-emiting layers in two p-i-n junctions, both the color and brightness of the resulting white OLED can be tuned independently by changing the positive and negative amplitudes of the AC voltage. © 2013 Elsevier B.V. All rights reserved

A bright cadmium-free, hybrid organic/quantum dot white light-emitting diode

We report a bright cadmium-free, InP-based quantum dot light-emitting diode (QD-LED) with efficient green emission. A maximum brightness close to 700 cd/m2 together with a relatively low turn-on voltage of 4.5 V has been achieved. With the design of a loosely packed QD layer resulting in the direct contact of poly[N,N′-bis(4-butylphenyl)-N,N′-bis(phenyl) benzidine] (poly-TPD) and 2,2′,2″-(1,3,5-benzinetriyl)-tris(1- phenyl-1-H-benzimidazole) (TPBi) in the device, a ternary complementary white QD-LED consisting of blue component (poly-TPD), green component (QDs), and red component (exciplex formed at the interface between poly-TPD and TPBi) has been demonstrated. The resulting white QD-LED shows an excellent color rendering index of 95. © 2012 American Institute of Physics

Implementation of Grid-connected PV Plant in remote location in Sumbawa Island of Indonesia: Lesson learned

The National Energy Policy (NEP) set 23% renewable energy target in the generation mix by 2025, where solar PV has identified as one of the feasible resources. There are many solar programs implemented in Indonesia. A large scale grid-connected solar PV (1 MW) project in Indonesia is analyzed in this study. The power plant is installed on Sumbawa island. The project is analyzed to investigate the performance of PV systems in a tropical climate. The performances were analyzed on project development, plants technical specification, energy production and performance index, and its current status. Data is collected through site visit and observations, documents review, and discussion with relevant stakeholders. PVSyst is used to simulate the potential of annual energy production and performance. Our audit found that the main components of the power plant are certified from reputable international organizations including Indonesian national standards. The simulation showed the power plant could generate 1,195 MWh annual energy with an average of 8% monthly variation which leads to an average performance index of 68.9%. Since the commissioning tests, the plant has not been operated. Consequently, no energy has been injected into the grid nor supplied to local load. Currently, the power plant is an inoperable condition due to non-technical problems. The problems are discussed, and a recommendation is presented in this paper