• Title/Summary/Keyword: electron injection layer

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The Effect of Electron Injection Layer in Organic Electroluminescence Device Efficiency (전자 주입층이 유기EL소자 효율에 미치는 영향)

  • Choi, Kyung-Hoon;Sohn, Byung-Chung;Kim, Young-Kwan
    • Journal of the Korean Applied Science and Technology
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    • v.19 no.4
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    • pp.297-301
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    • 2002
  • We investigated the effect of electron injection layer on the performance of organic light emitting devices (OLEDs). As an electron injection layer, the quinolate metal complexes were used. We optimized the device efficiency by varying the thickness of the quinolate metal complexes layer. The device with 1 nm of the quinolate metal complexes layer showed significant enhancement of the device performance and device lifetime. We also compared the effect of 8-hydroxyquinolinolatolithium (Liq) with that of bis(8-quinolinolato)-zinc ($Znq_{2}$) and 8-hydroxyquinolinolatosodium (Naq) as an electron injection layer. As a result, Liq is considered as a better materials for the electron injection layer than $Znq_{2}$ and Naq.

Electrical Properties of OLEDs depending on Thickness variation of Electron Injection Layer (전자 주입층의 두께 변화에 따른 OLEDs의 전기적 특성)

  • Cha, Ki-Ho;Lee, Young-Hwan;Lee, Jong-Yong;Chung, Dong-Hoe;Shin, Jong-Yeol;Kim, Tae-Wan;Hong, Jin-Woong
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2006.06a
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    • pp.69-70
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    • 2006
  • We studied increasement of efficiency of Organic Light-emitting Diodes depending on thickness variation of LiF, Material of Electron Injection Layer in structure of ITO/Hole Injection Layer (PTFE)/Hole Transportion Later (TPD)/Emitting Layer (Alq3)/Electron Injection Layer (LiF)/Al. TPD and $Alq_3$ is deposited as rate of 1.3~1.5 [${\AA}/s$] in high vacuum ($5{\times}10^{-6}$ [torr]). In result of these studies, we can know maximum efficiency in 0.7 [nm], thickness of LiF. And samples with electron injection material are increased about 5-fold in maximum efficiency in compare with sample without electron injection material.

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CHARACTERISTICS OF ORGANIC LIGHT-EMITTING DIODES FOR THE DEVICES WITH ELECTRON INJECTION LAYER (LIF AND $LI_2O$) (전자주입층(LiF와 $Li_2O$)을 사용한 유기 발광 소자의 특성)

  • Shin, Eun-Chul;An, Hui-Chul;Lee, Ho-Sik;Song, Min-Jong;Lee, Won-Jae;Han, Wone-Keun;Kim, Tae-Wan
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2007.06a
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    • pp.439-440
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    • 2007
  • To enhance the electron injection from the cathode of organic light-emitting diodes (OLEDs), We have studied characteristics of device that electron injection layer(EIL) is inserted between emissive layer and cathode. We fabricated bi-layer cathode $Li_2O$(x nm)/Al(100nm) and LiF(x nm)/Al(100nm) using LiF and $Li_2O$ as an electron injection layer. We analyzed the current efficiency, luminance efficiency, and external quantum efficiency of the device by varying the thickness of $Li_2O$ and LiF to be 0.5nm, 1nm, or 3nm. Using the EIL, we have obtained the efficiency of 7cd/A and the luminance of $20,000cd/m^2$. There is an improvement of efficiency by more than 3 times than the device without the $Li_2O$ layer.

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Improved Electron Injection on Organic Light-emitting Diodes with an Organic Electron Injection Layer

  • Kim, Jun-Ho;Suh, Chung-Ha;Kwak, Mi-Young;Kim, Bong-Ok;Kim, Young-Kwan
    • Transactions on Electrical and Electronic Materials
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    • v.6 no.5
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    • pp.221-224
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    • 2005
  • To overcome of poor electron injection in organic light-emitting diodes (OLEDs) with Al cathode, a thin layer of inorganic insulating materials, like as LiF, is inserted between an Al cathode and an organic electron transport layer. Though the device, mentioned above, improves both turn on voltage and luminescent properties, it has some problems like as thickness restriction, less than 2 nm, and difficulty of deposition control. On the other hand, Li organic complex, Liq, is less thickness restrictive and easy to deposit and it also enhances the performance of devices. This paper reports the improved electron injection on OLEDs with another I A group metal complex, Potassium quinolate (Kq), as an electron injection material. OLEDs with organic complexes showed improved turn-on voltage and luminous efficiency which are remarkably improved compared to OLEDs with Al cathode. Especially, OLEDs with Kq have longer life time than OLEDs with Liq.

Study of OLED luminescence efficiency by electron Injection layer change (유기발광 소자의 전자 주입층 두께 변화에 따른 발광효율 연구)

  • Lee, Jung-Ho
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2004.11a
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    • pp.555-558
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    • 2004
  • The efficiency of electron injection from the cathode is strongly dependent on the thickness of the LiF buffer-layer. We used LiF to electron Injection layer. We compared characteristics of organic light emitting device changing LiF thin film thickness from 1.0 m to 10.0 nm. Experiment result, we found that LiF thickness has the optimized electrical characteristics in 3.0 m. In this paper, we did research about electrical characteristics of organic light emitting device by LiF thickness change using method numerical analysis method. We proved adequate experimental results that compare results of numerical analysis, and come out through an experiment results is validity.

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Interfacial Electronic Structures for Electron and Hole Injection in Organic Devices: Nanometer Layers of CsN3 and 1,4,5,8,-naphthalene-tetracarboxylic-dianhydride (NTCDA)

  • Yi, Yeon-Jin;Jeon, Pyeongeu;Lee, Jai-Hyun;Jeong, Kwang-Ho;Kim, Jeong-Won
    • Proceedings of the Korean Vacuum Society Conference
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    • 2012.02a
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    • pp.90-90
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    • 2012
  • The electron/hole injections in organic electronic devices have long been an issue due to the large energy level mismatches between electrode and organic layer. To utilize the organic materials in electronic devices, functional thin layers have been used, which reduce the electron/hole injection barrier from electrode to organic material. Typically, inorganic compounds and organic molecules are used as an electron and hole injection layer, respectively. Recently, CsN3 and 1,4,5,8,- naphthalene-tetracarboxylic-dianhydride (NTCDA) are reported as a potential electron and hole injection layers. CsN3 shows unique properties that it breaks into Cs and N and thus Cs can dope organic layer into n-type. On the other side, hole injection anode, NTCDA forms gap states with anode material. In this presentation, we show the electronic structure changes upon the insertion of CsN3 and NTCDA at proper interfaces to reduce the charge injection barriers. These barrier reductions are correlated with device characteristics.

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Efficiency and Lifetime Improvement of Organic Light- Emitting Diodes with a Use of Lithium-Carbonate- Incorportated Cathode Structure

  • Mok, Rang-Kyun;Kim, Tae-Wan
    • Transactions on Electrical and Electronic Materials
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    • v.13 no.2
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    • pp.60-63
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    • 2012
  • Enhancement of efficiency and luminance of organic light-emitting diodes was investigated by the introduction of a lithium carbonate ($Li_2CO_3$) electron-injection layer. Electron-injection layer is used in organic light-emitting diodes to inject electrons efficiently between a cathode and an organic layer. A device structure of ITO/TPD (40 nm)/$Alq_3$ (60 nm)/$Li_2CO_3$ (x nm)/Al (100 nm) was manufactured by thermal evaporation, where the thickness of $Li_2CO_3$ layer was varied from 0 to 3.3 nm. Current density-luminance-voltage characteristics of the device were measured and analyzed. When the thickness of $Li_2CO_3$ layer is 0.7 nm, the current efficiency and luminance of the device at 8.0 V are improved by a factor of about 18 and 3,000 compared to the ones without the $Li_2CO_3$ layer, respectively. The enhancement of efficiency and luminance of the device with an insertion of $Li_2CO_3$ electron-injection layer is thought to be due to the lowering of an electron barrier height at the interface region between the cathode and the emissive layer. This is judged from an analysis of current density-voltage characteristics with a Fowler-Nordheim tunneling conduction mechanism model. In a study of lifetime of the device that depends on the thickness of $Li_2CO_3$ layer, the optimum thickness of $Li_2CO_3$ layer was obtained to be 1.1 nm. It is thought that an improvement in the lifetime is due to the prevention of moisture and oxygen by $Li_2CO_3$ layer. Thus, from the efficiency and lifetime of the device, we have obtained the optimum thickness of $Li_2CO_3$ layer to be about 1.0 nm.

Improved performance of n-type organic field-effect transistor with a non-conjugated polyelectrolyte layer

  • Park, Yu Jung;Cha, Myoung Joo;Lee, Jin Hee;Cho, Shinuk;Seo, Jung Hwa;Walker, Bright
    • Proceedings of the Korean Vacuum Society Conference
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    • 2016.02a
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    • pp.151.2-151.2
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    • 2016
  • We characterized the n-type organic field-effect transistors (OFETs) with non-conjugated polyelectrolytes (NPEs) interlayers as the electron injection layer. Novel NPEs with various ions (Cl-, Br-, I-) improved the electron mobility from $5.06{\times}10^{-3}$ to $2.10{\times}10^{-2}cm^2V^{-1}s^{-1}$ in OFETs based [6,6]-Phenyl-$C_{61}$-butyric acid methyl ester (PCBM) when $PEIEH^+I^-$ spin-cast from 0.6% solution was deposited onto the PCBM layer. Reduced electron injection barrier (${\phi}_e$) at NPE/metal electrode interface was induced by dipole formation and led to increase the electron injection and transport. These findings are important for understanding how NPEs function in devices, the improvement of device performance, and the design of new materials for use in optoelectronic devices.

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Lithium Quinolate Complex as an Electron Injection Layer in Organic Light Emitting Devices

  • Choi, Kyung-Hoon;Kim, Young-Kwan;Sohn, Byung-Chung;Ha, Yun-Kyung;Kim, Sung-Min;Kim, Bong-Ok;Kwak, Mi-Young;Cho, Young-Jun
    • 한국정보디스플레이학회:학술대회논문집
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    • 2002.08a
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    • pp.706-709
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    • 2002
  • We investigated the effect of lithium 8-hydroxyquinolinolatolithium (Liq) as an electron injection layer on the performance of organic light emitting devices (OLEDs) and optimized the device efficiency by varying thickness of Liq layer. The device with 1nm Liq layer showed significant enhancement of the device performance and device lifetime. We also compared $Znq_2$ and LiBBOX with Liq as an electron injection layer.

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Development of Blue Organic Light-Emitting Diodes(OLEDs) Due to Change in Mixed Ratio of HTL:EML(DPVBi:NPB) Layers (HTL:EML(DPVBi:NPB) 층의 조성비 변화에 따른 청색 유기 발광 소자 개발)

  • Lee, Tae-Sung;Lee, Byoung-Wook;Hong, Chin-Soo;Kim, Chang-Kyo
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2008.04a
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    • pp.31-32
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    • 2008
  • The structure of OLEDs with conventional heterostructure consists of anode, hole injection layer, hole transport layer, light-emitting layer, electron transport layer, electron injection layer, and cathode. NPB used as a hole transport layer and DPVBi used as a blue light emitting layer were graded-mixed at selected ratio. Interface at heterojunction between the hole transport layer and the elecrtron transport layer restricts device's stability. Mixing of the hole transport layerand the emitting layer removes abrupt interface between the hole transport. layer and the electron transport layer. The stability of OLED with graded mixed-layer developed in this study was improved.

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