scholarly journals Improved Efficiency of Perovskite Light-Emitting Diodes Using a Three-Step Spin-Coated CH3NH3PbBr3 Emitter and a PEDOT:PSS/MoO3-Ammonia Composite Hole Transport Layer

Micromachines ◽  
2019 ◽  
Vol 10 (7) ◽  
pp. 459 ◽  
Author(s):  
Yuanming Zhou ◽  
Sijiong Mei ◽  
Dongwei Sun ◽  
Neng Liu ◽  
Wuxing Shi ◽  
...  
Keyword(s):  
Current Efficiency ◽  
High Efficiency ◽  
Light Emitting Diodes ◽  
Control Device ◽  
Hole Transport ◽  
Transport Layer ◽  
Hole Injection ◽  
Maximum Luminance ◽  
Light Emitting ◽  
Maximum Current

High efficiency perovskite light-emitting diodes (PeLEDs) using PEDOT:PSS/MoO3-ammonia composite hole transport layers (HTLs) with different MoO3-ammonia ratios were prepared and characterized. For PeLEDs with one-step spin-coated CH3NH3PbBr3 emitter, an optimal MoO3-ammonia volume ratio (0.02) in PEDOT:PSS/MoO3-ammonia composite HTL presented a maximum luminance of 1082 cd/m2 and maximum current efficiency of 0.7 cd/A, which are 82% and 94% higher than those of the control device using pure PEDOT:PSS HTL respectively. It can be explained by that the optimized amount of MoO3-ammonia in the composite HTLs cannot only facilitate hole injection into CH3NH3PbBr3 through reducing the contact barrier, but also suppress the exciton quenching at the HTL/CH3NH3PbBr3 interface. Three-step spin coating method was further used to obtain uniform and dense CH3NH3PbBr3 films, which lead to a maximum luminance of 5044 cd/m2 and maximum current efficiency of 3.12 cd/A, showing enhancement of 750% and 767% compared with the control device respectively. The significantly improved efficiency of PeLEDs using three-step spin-coated CH3NH3PbBr3 film and an optimum PEDOT:PSS/MoO3-ammonia composite HTL can be explained by the enhanced carrier recombination through better hole injection and film morphology optimization, as well as the reduced exciton quenching at HTL/CH3NH3PbBr3 interface. These results present a promising strategy for the device engineering of high efficiency PeLEDs.

Balancing Charge Injection and Transport in Organic Light-emitting Diodes with a Transparent Conductive Tungsten Oxide Layer

2014 ◽  
Vol 1629 ◽  
Author(s):  
R. Acharya ◽  
X. M. Li ◽  
Y. Lu ◽  
X. A. Cao
Keyword(s):  
Current Efficiency ◽  
Light Emitting Diodes ◽  
Charge Injection ◽  
Hole Transport ◽  
Organic Light Emitting Diodes ◽  
Transport Layer ◽  
Hole Injection ◽  
Hole Transport Layer ◽  
Light Emitting ◽  
Organic Light

ABSTRACTHigh-brightness green phosphorescent hybrid inorganic-organic light-emitting diodes (HyLEDs) and inverted HyLEDs (IHyLEDs) have been demonstrated. The devices comprised a transparent and conductive WO3 layer deposited by thermal evaporation, which improved both hole injection and transport, and led to more balanced charge injection and significant performance enhancement. At 20 mA/cm2, the HyLEDs had a low operation voltage of 6.1 V, 0.8 V lower than that of OLEDs with an organic hole transport layer. With an optimized layer structure, the HyLEDs reached 104 cd/m2 brightness at 7.3 V. At this brightness level, the current efficiency was 55.2 cd/A, 57% higher than that of the OLEDs. In the IHyLEDs, facile hole injection and transport through WO3 was balanced by electron injection from the indium-tin-oxide (ITO) cathode overcoated with nanometer-thick Ca, leading to a low turn-on voltage of ∼6 V. Brightness of 8133 cd/m2 was reached at 20 mA/cm2 and the corresponding current efficiency was 40 cd/A. The hybrid devices also exhibited markedly improved stability under constant-current stressing due to the robust WO3 hole transport layer.

Efficient quasi-two dimensional perovskite light-emitting diodes using a cage-type additive

2020 ◽  
Vol 8 (29) ◽  
pp. 9845-9853
Author(s):  
Run Wang ◽  
Yue Zhang ◽  
Xing-Juan Ma ◽  
Yan-Hong Deng ◽  
Jun-Wei Shi ◽  
...  
Keyword(s):  
Current Efficiency ◽  
High Performance ◽  
Light Emitting Diodes ◽  
Hole Transport ◽  
Type Structure ◽  
Transport Layer ◽  
Hole Transport Layer ◽  
Two Dimensional ◽  
Light Emitting ◽  
Maximum Current

High performance quasi-2D PeLEDs with maximum current efficiency of 35.5 cd A−1, by introducing α-cyclodextrin (α-CD) with a cage-type structure as an additive and TFB/PVK bilayer as a hole transport layer, are demonstrated.

scholarly journals Enhanced hole injection assisted by electric dipoles for efficient perovskite light-emitting diodes

2020 ◽  
Vol 1 (1) ◽  
Author(s):  
Xiangtian Xiao ◽  
Kai Wang ◽  
Taikang Ye ◽  
Rui Cai ◽  
Zhenwei Ren ◽  
...  
Keyword(s):  
Electric Dipole ◽  
Light Emitting Diodes ◽  
Hole Transport ◽  
Transport Layer ◽  
Hole Injection ◽  
Hole Transport Layer ◽  
Light Emitting ◽  
Hole Injection Layer ◽  
Dipole Layer ◽  
Electric Dipoles

Abstract Enhanced hole injection is essential to achieve high performance in perovskite light-emitting diodes (LEDs). Here, a strategy is introduced to enhance hole injection by an electric dipole layer. Hopping theory demonstrates electric dipoles between hole injection layer and hole transport layer can enhance hole injection significantly. MoO3 is then chosen as the electric dipole layer between PEDOT:PSS (hole injection layer) and PVK (hole transport layer) to generate electric dipoles due to its deep conduction band level. Theoretical results demonstrate that strong electric fields are produced for efficient hole injection, and recombination rate is substantially increased. Capacitance-voltage analyses further prove efficient hole injection by introducing the electric dipole layer. Based on the proposed electric dipole layer structure, perovskite LEDs achieve a high current efficiency of 72.7 cd A−1, indicating that electric dipole layers are a feasible approach to enhance perovskite LEDs performance.

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 Effects of Charge Transport Materials on Blue Fluorescent Organic Light-Emitting Diodes with a Host-Dopant System

Micromachines ◽  
2019 ◽  
Vol 10 (5) ◽  
pp. 344 ◽  
Author(s):  
Neng Liu ◽  
Sijiong Mei ◽  
Dongwei Sun ◽  
Wuxing Shi ◽  
Jiahuan Feng ◽  
...  
Keyword(s):  
Electron Transport ◽  
High Efficiency ◽  
Light Emitting Diodes ◽  
Molybdenum Trioxide ◽  
Hole Transport ◽  
Organic Light Emitting Diodes ◽  
Maximum Luminance ◽  
Light Emitting ◽  
Organic Light ◽  
Hole Transport Layers

High efficiency blue fluorescent organic light-emitting diodes (OLEDs), based on 1,3-bis(carbazol-9-yl)benzene (mCP) doped with 4,4’-bis(9-ethyl-3-carbazovinylene)-1,1’-biphenyl (BCzVBi), were fabricated using four different hole transport layers (HTLs) and two different electron transport layers (ETLs). Fixing the electron transport material TPBi, four hole transport materials, including 1,1-Bis[(di-4-tolylamino)phenyl]cyclohexane (TAPC), N,N’-Di(1-naphthyl)-N,N’-diphenyl-(1,1’-biphenyl)-4’-diamine(NPB), 4,4’-Bis(N-carbazolyl)-1,1,-biphenyl (CBP) and molybdenum trioxide (MoO3), were selected to be HTLs, and the blue OLED with TAPC HTL exhibited a maximum luminance of 2955 cd/m2 and current efficiency (CE) of 5.75 cd/A at 50 mA/cm2, which are 68% and 62% higher, respectively, than those of the minimum values found in the device with MoO3 HTL. Fixing the hole transport material TAPC, the replacement of TPBi ETL with Bphen ETL can further improve the performance of the device, in which the maximum luminance can reach 3640 cd/m2 at 50 mA/cm2, which is 23% higher than that of the TPBi device. Furthermore, the lifetime of the device is also optimized by the change of ETL. These results indicate that the carrier mobility of transport materials and energy level alignment of different functional layers play important roles in the performance of the blue OLEDs. The findings suggest that selecting well-matched electron and hole transport materials is essential and beneficial for the device engineering of high-efficiency blue OLEDs.

scholarly journals Regulation of hole transport layer for perovskite quantum dot light-emitting diodes

2021 ◽  
Vol 245 ◽  
pp. 03021
Author(s):  
Ronghong Zheng ◽  
Dong Huang ◽  
Dongyang Shen ◽  
Chengzhao Luo ◽  
Yu Chen
Keyword(s):  
Quantum Dots ◽  
Quantum Dot ◽  
Light Emitting Diodes ◽  
Hole Transport ◽  
Transport Layer ◽  
Hole Injection ◽  
Hole Transport Layer ◽  
Emission Layer ◽  
Light Emitting ◽  
Hole Injection Layer

Perovskite quantum dots have been widely used in light-emitting diodes (LEDs) because of their adjustable color, high quantum yield and easy solution processing. Furthermore, matching energy levels of device plays a profound role in the resultant LEDs. In this study, a polymeric material, namely poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(4,4’-(N-(pbutylphenyl))diphenylamine)] (TFB), is introduced between the quantum dot emission layer and the hole injection layer PEDOT:PSS, which not only prevents the fluorescence quenching caused by the direct contact between the perovskite layer and the hole injection layer, but also reduces hole injection barrier, both being beneficial to the device performance. The optimal thickness of TFB has been obtained by adjusting the rotational speed and precursor solution concentration during spin coating. The optimized quantum dots LED has a switching on voltage of about 2.2 V, a maximum brightness of 4300 cd/m2, a maximum external quantum efficiency of 0.15%, and a maximum current density of 0.54 cd/A.

scholarly journals High efficiency green InP quantum dot light-emitting diodes by balancing electron and hole mobility

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Wei-Chih Chao ◽  
Tzu-Hsuan Chiang ◽  
Yi-Chun Liu ◽  
Zhi-Xuan Huang ◽  
Chia-Chun Liao ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Quantum Dot ◽  
High Efficiency ◽  
Light Emitting Diodes ◽  
Hole Mobility ◽  
Hole Transport ◽  
Transport Layer ◽  
Electron Transport Layer ◽  
Light Emitting ◽  
A Current

AbstractThe industrialization of quantum dot light-emitting diodes (QLEDs) requires the use of less hazardous cadmium-free quantum dots, among which ZnSe-based blue and InP-based green and red quantum dots have received considerable attention. In comparison, the development of InP-based green QLEDs is lagging behind. Here, we prepare green InP/ZnSe/ZnS quantum dots with a diameter of 8.6 nm. We then modify the InP quantum dot emitting layer by passivation with various alkyl diamines and zinc halides, which decreases electron mobility and enhances hole transport. This, together with optimizing the electron transport layer, leads to green 545 nm InP QLEDs with a maximum quantum efficiency (EQE) of 16.3% and a current efficiency 57.5 cd/A. EQE approaches the theoretical limit of InP quantum dots, with an emission quantum yield of 86%.

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