• Title/Summary/Keyword: external quantum efficiency

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The Effect of Sulfurization Temperature on CuIn(Se,S)2 Solar Cells Synthesized by Electrodeposition

  • Kim, Dong-Uk;Yun, Sang-Hwa;Yu, Bong-Yeong
    • Proceedings of the Korean Institute of Surface Engineering Conference
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    • 2014.11a
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    • pp.97-97
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    • 2014
  • The properties of thin film solar cells based on electrodeposited $CuIn(Se,S)_2$ were investigated. The proposed solar cell fabrication method involves a single-step $CuInSe_2$ thin film electrodeposition followed by sulfurization in a tube furnace to form a $CuIn(Se,S)_2$ quaternary phase. A sulfurization temperature of $450-550^{\circ}C$ significantly affected the performance of the $CuIn(Se,S)_2$ thin film solar cell in addition to its composition, grain size and bandgap. Sulfur(S) substituted for selenium(Se) at increasing rates with higher sulfurization temperature, which resulted in an increase in overall band gap of the $CuIn(Se,S)_2$ thin film. The highest conversion efficiency of 3.12% under airmass(AM) 1.5 illumination was obtained from the $500^{\circ}C$-sulfurized solar cell. The highest External Quantum Efficiency(EQE) was also observed at the sulfurization temperature of $500^{\circ}C$.

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New Blue Emitting Indenopyrazine Derivatives for OLEDs : Improving the EL Properties Through Substitution Effects by Using Terphenyl Side Group

  • Park, Young-Il;Seok, Chang-Hun;Lee, Ji-Hoon;Jaung, Jae-Yun;Park, Jong-Wook
    • 한국정보디스플레이학회:학술대회논문집
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    • 2009.10a
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    • pp.798-802
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    • 2009
  • New blue emitting materials of o,p-TP-EPY and m,m-TP-EPY were synthesized using two terphenyl units with different structures in the new core of indenopyrazine. EL spectrum of o,p-TP-EPY was more blue shifted than m,m-TP-EPY, and external quantum efficiency of o,p-TP-EPY was showed improvement of about 60% compared to efficiency of m,m-TP-EPY.

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Emission Characteristics of White PHOLEDs with Different Emitting Layer Structures (발광층 구조에 따른 백색 인광 OLED의 발광 특성)

  • Seo, Jung-Hyun;Paek, Kyeong-Kap;Ju, Sung-Hoo
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.25 no.6
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    • pp.456-461
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    • 2012
  • We studied the emission characteristics of white phosphorescent organic light-emitting diodes (PHOLEDs), which were fabricated using a two-wavelength method. To optimize emission characteristics of white PHOLEDs, white PHOLEDs with red/blue, blue/red and red/blue/red emitting layer (EML) structures were fabricated using a host-dopant system. In case of white PHOLEDs with red/blue structure, the best efficiency was obtained at a structure of red (15 nm)/blue (15 nm). But the emission color was blue-shifted white. In case of white PHOLEDs with blue/red structure, the better color purity and efficiency were observed at a blue (29 nm)/red (1 nm) structure. For additional improvement of color purity in white PHOLEDs with blue (29 nm)/red (1 nm) EMLs, we fabricated white PHOLEDs with red (1 nm)/blue (28 nm)/red (1 nm) structure. The current efficiency, external quantum efficiency, and CIE (x, y) coordinate were 27.2 cd/A, 15.1%, and (0.382, 0.369) at 1,000 $cd/m^2$, respectively.

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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Analysis of Stress-Induced Effect in Blue GaN-Based Light-Emitting Diodes (질화갈륨 기반 청색 고체 발광 다이오드에서의 스트레스 영향 해석)

  • Shim, Sang Kyun;Lee, June Key;Kim, Youngman
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.32 no.6
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    • pp.444-447
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    • 2019
  • It was proven that the light outputs of blue GaN-based light-emitting diodes (LEDs) was seriously influenced by the application of external stress. We have simulated the wave function overlap of an electron and hole, which are significantly reduced by the development of stress. Consequently, its internal quantum efficiency decreased from 67.0% to 37.5%. To experimentally investigate the effect of stress, we designed and prepared a special zig system. By applying external tensile stress to compensate for the compressive stress innately developed in Blue LEDs, it was found that the optical output was greatly enhanced from 83.1 mcd to 117.2 mcd at a current of 100 mA, an increase of approximately 41%. In contrast, when the compressive stress is developed more by external compressive stress, we observed that the light output power was reduced from 89.0 mcd to 80.7 mcd, a decrease of approximately 9.3%.

A Study on the Improvement of Light-Extraction Efficiency of Organic Light-Emitting Diodes with a Use of Random-Textured Film (랜덤 택스쳐 필름을 이용한 유기 발광 소자의 광추출 효율 향상에 관한 연구)

  • Kim, Hye Sook;Hwang, Deok Hyeon;Jang, Kyeong Uk;Kim, Tae Wan
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.28 no.7
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    • pp.446-449
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    • 2015
  • An improvement of light-extraction efficiency of organic light-emitting diodes was studied by using random-textured films (RTF). Device was made in a structure of RTF/glass/ITO/TPD/$Alq_3$/LiF/Al. RTF mold was made by spreading PDMS solution on a sandpaper. By pressing this mold on the glass substrate pre-coated with ZPU material, the RTF was obtained. From this study, there was an improvement of external quantum efficiency by about 30% in the device with the random-textured film (RTF 40) compared to that of the reference one.

Emission Characteristics of White OLEDs with Various Hole Transport Layers (정공수송층에 따른 백색 OLED의 발광 특성)

  • Lim, Byung-Gwan;Seo, Jung-Hyun;Ju, Sung-Hoo;Paek, Kyeong-Kap
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.23 no.12
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    • pp.983-987
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    • 2010
  • In order to investigate the emission characteristics of the phosphorescent white organic light-emitting diodes (PHWOLEDs) according to various hole transport layers (HTLs), PHWOLEDs composed of HTLs whose structure are NPB/TCTA, NPB/mCP and NPB/TCTA/mCP, two emissive layers (EMLs) which emit two-wavelengths of light (blue and red), and electron transport layer were fabricated. The applied voltage, power efficiency, and external quantum efficiency at a current density of $1 mA/cm^2$ for the fabricated PHWOLEDs were 7.5 V, 11.5 lm/W, and 15%, in case of NPB/mCP, 5 V, 14.8 lm/W, and 13.7%, in case of NPB/TCTA, and 5.5 V, 14.6 lm/W, and 15%, in case of NPB/TCTA/mCP in the hole transport layer, respectively. High emission efficiency can be obtained when the amount of hole injection from anode is balanced out by the amount of electron injection from the cathode to EML by using NPB/TCTA/mCP structured HTL.

Efficiency Improvement of OLEDs with a Variation of Cathodes (음전극 변화에 따른 유기 발광 소자의 효율 향상)

  • Kim, S.K;Chung, D.H.;Chung, T.G.;Lee, H.S.;Jang, K.U.;Choi, M.G.;Hong, Jin-Ung;Lee, J.U.;Kim, T.W.
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2002.07b
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    • pp.1038-1041
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    • 2002
  • We have investigated the effects of cathode in organic light-emitting diodes of ITO/TPD/$Alq_3$/Cathodes(Al, LiF/Al, Ca/Al, and LiAl) by measuring current-voltage-luminance characteristics. The device with cathodes other than Al cathode shows the efficiency by an oder of one compared with Al cathode only. This improvement is due to a reduction of barrier height in cathode side.

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Efficient Organic Light-emitting Diodes using Hole-injection Buffer Layer

  • Chung, Dong-Hoe;Kim, Sang-Keol;Lee, Joon-Yng;Hong, Jin-Woong;Cho, Hyun-Nam;Kim, Young-Sik;Kim, Tae-Wan
    • Journal of Information Display
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    • v.4 no.1
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    • pp.29-33
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    • 2003
  • We have investigated the effects of hole-injection buffer layer in organic light-emitting diodes using copper phthalocyanine (CuPc), poly(vinylcarbazole)(PVK), and Poly(3,4-ethylene dioxythiophene):poly(styrenesulfonate) (PEDOT: PSS) in a device structure of $ITO/bufferr/TPD/Alq_3/Al$. Polymer PVK and PEDOT:PSS buffer layer were produced using the spin casting method where as the CuPc layer was produced using thermal evaporation. Current-voltage characteristics, luminance-voltage characteristics and efficiency of device were measured at room temperature at various a thickness of the buffer layer. We observed an improvement in the external quantum efficiency by a factor of two, four, and two and half when the CuPc, PVK, and PEDOT:PSS buffer layer were used, respectively. The enhancement of the efficiency is assumed to be attributed to the improved balance of holes and elelctrons resulting from the use of hole-injection buffer layer. The CuPc and PEDOT:PSS layer function as a hole-injection supporter and the PVK layer as a hole-blocking one.

White OLEDs with a Single Emissive Layer (단일발광층을 이용한 백색 OLED)

  • Chu, Hye-Yong;Lee, Jeong-Ik;Yang, Yong-Suk;Oh, Ji-Young;KoPark, Sang-Hee;Kim, Mi-Kyung;Hwang, Chi-Sun;Jung, Byung-Jun;Shim, Hong-Ku;Jang, Jin
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2004.05a
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    • pp.43-46
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    • 2004
  • We demonstrated efficient white light emitting OLEDs with a single emissive layer structure, which was blue-emitting 1,4-bis[2,2-diphenylvinyl]biphenyl (DPVBi) doped with blue luminescent amino-substituted distyrylarylene amine (DSA-amine) and red luminescent [2,6-bis[2-[5-(dibutylamino) phenyl]vinyl]-4H -pyran-4-ylidene]propanedinitrile (DADB). Through the optimization of the device structure, the white light emission with full visible spectral range was obtained. Its CIE color coordinates was (0.32,0.42) at 10 $mA/cm^2$ and the external quantum efficiency, the luminance efficiency and the luminance yield were 3.7 %, 3.3 lm/W and 9.0 cd/A, respectively.

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