• Title/Summary/Keyword: external quantum efficiency

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Fabrication of High Power $Al_{0.07}$$Ga_{0.93}$As Laser Diode Array) (고출력 $Al_{0.07}$$Ga_{0.93}$As 레이저 다이오드 어레이 제작)

  • 손노진;박성수;안정작;권오대;계용찬;정지채;최영수;강응철;김재기
    • Journal of the Korean Institute of Telematics and Electronics A
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    • v.32A no.10
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    • pp.43-50
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    • 1995
  • A laser diode(LD) structure consisting of a single 150$\AA$ $Al_{0.07}$Ga$_{0.93}$As quantum well active region operating at ${\lambda}$=809nm, cladded with an AlGaAs graded-index separate confinement heterostructure, has bes been grown by MOCVD. Temperature coefficient of wavelength is approximately 0.2nm $^{\circ}C$ for the diode. The active aperture consists of five emitters separated from each other by means of SiO$_{2}$ deposition and stripe formation, which creates insulating regions that channel the current to 100-$\mu$m-wide stripes placed on 450-$\mu$m centers. From a typical uncoated LD, the output power of 0.8W has been obtained at a 1$\mu$s, 1kHz pulsed current level of 2.0$\AA$, which results in about 64% external quantum efficiency. The threshold current density is 736A/cm$^{2}$ for the case of 500$\mu$m cavity length LD's. The measure of an internal quantum efficiency was 75.8% and the internal loss 4.83$cm^{-1}$ . Finally, 3.1W output power has been obtained at a 1$\mu$s, 1kHz pulsed current level of 9A from the 500$\mu$m-aperture LD array with 460-$\mu$m- cavity length.

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Performance Improvement of Flexible Thin Film Si Solar Cells using Graphite Substrate (그라파이트 기판을 이용한 유연 박막 실리콘 태양전지 특성 향상)

  • Lim, Gyeong-yeol;Cho, Jun-sik;Chang, Hyo Sik
    • Korean Journal of Materials Research
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    • v.29 no.5
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    • pp.317-321
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    • 2019
  • We investigated the characteristics of nano crystalline silicon(nc-Si) thin-film solar cells on graphite substrates. Amorphous silicon(a-Si) thin-film solar cells on graphite plates show low conversion efficiency due to high surface roughness, and many recombination by dangling bonds. In previous studies, we deposited barrier films by plasma enhanced chemical vapor deposition(PECVD) on graphite plate to reduce surface roughness and achieved ~7.8 % cell efficiency. In this study, we fabricated nc-Si thin film solar cell on graphite in order to increase the efficiency of solar cells. We achieved 8.45 % efficiency on graphite plate and applied this to nc-Si on graphite sheet for flexible solar cell applications. The characterization of the cell is performed with external quantum efficiency(EQE) and current density-voltage measurements(J-V). As a result, we obtain ~8.42 % cell efficiency in a flexible solar cell fabricated on a graphite sheet, which performance is similar to that of cells fabricated on graphite plates.

Spike type high-transmittance external light extraction film imprinted with P(VDF-TrFE) mold with island surface structure (Island 표면구조의 P(VDF-TrFE) 몰드를 임프린트한 Spike 형태의 고투과성 외부광추출 필름)

  • Sung, Baeksang;Cho, Jae-Hyeok;Lim, Young-Ji;Gasonoo, Akpeko;Lee, Hyunah;Lee, Jangwon;Woo, Seungwan;Kim, Dongsoo;Lee, Jae-Hyun;Kim, Min-Hoi;Lee, Jonghee
    • Journal of IKEEE
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    • v.25 no.2
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    • pp.322-329
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    • 2021
  • In this study, a method for improving the light extraction efficiency of organic light emitting diodes was presented using the polymer Poly(vinylidenefluoride-co-trifluoroethylene) [P(VDF-TrFE)] having an island surface structure after annealing. Polydimethylsiloxane (PDMS) imprinted on the island-structured P(VDF-TrFE) surface has a spike structure, which improves the external light extraction efficiency aroud 20%. It was confirmed that the produced film showed a low haze characteristic of 8.2, and the Current and external quantum efficiency could be improved without pixel blur due to the excellent transmittance of 93.4%.

Novel transport materials for high-performance fluorescent and phosphorescent OLEDs

  • Bohm, E.;Anemian, R.;Busing, A.;Fortte, R.;Heil, H.;Kaiser, J.;Krober, J.;Leu, S.;Mujica-Fernaud, T.;Parham, A.;Pflumm, C.;Voges, F.
    • Journal of Information Display
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    • v.12 no.3
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    • pp.141-144
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    • 2011
  • To improve the performance of blue fluorescent and green phosphorescent organic light-emitting diode devices, Merck developed novel green phosphorescent host and electron-transporting materials. The newly developed electron-transporting material improves the external quantum efficiency of blue fluorescent devices up to 8.7%, with an excellent lifetime. In combination with the newly developed host materials, the efficiency of green phosphorescent devices can be improved by a factor of 1.7, and the lifetime by a factor of 7.

Highly efficient white organic light-emitting diodes using hybrid-spacer or/and codoped blue emitting layers

  • Seo, Ji-Hoon;Kim, Gu-Young;Hyung, Gun-Woo;Lee, Kum-Hee;Kim, You-Hyun;Kim, Woo-Young;Yoon, Seung-Soo;Kim, Young-Kwan
    • 한국정보디스플레이학회:학술대회논문집
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    • 2008.10a
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    • pp.1219-1221
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    • 2008
  • The Authors have demonstrated highly efficient white organic light-emitting diodes using hybrid-spacer which was inserted between each emitting layer or/and codoped blue emitting layers with the different functional material. The characteristics of WOLEDs showed the maximum external quantum efficiency of 13.8%, power efficiency of 33.66 lm/W, and Commission Internationale de I'Eclairage coordinates of (x=0.36, y=0.37), respectively.

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Efficient, Color Stable White Organic Light-Emitting Diode Based on High Energy Level Dopant

  • Park, Young-Seo;Kang, Dong-Min;Park, Jong-Won;Kwon, Soon-Ki;Kang, Jae-Wook;Kim, Yun-Hi;Kim, Jang-Joo
    • 한국정보디스플레이학회:학술대회논문집
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    • 2008.10a
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    • pp.1120-1123
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    • 2008
  • Efficient, color stable multi-EML WOLED have been fabricated using newly synthesized yellowish green dopant Ir(chpy)3 or Ir(mchpy)3. The devices have high external quantum efficiency of 11.7%, color rendering index of 87, variation of CIE coordinate of (0.02, 0.01) between 10 to 5000 cd/m2, and low roll-off in efficiency with increasing brightness.

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Molecular Engineering of Blue Organic Light Emitting Materials Based on Diarylamino-fluorene

  • Lee, Kum-Hee;Kwon, Young-Soo;Kang, Lee-Kyung;Kim, Gu-Young;Seo, Ji-Hoon;Kim, Young-Kwan;Yoon, Seung-Soo
    • 한국정보디스플레이학회:학술대회논문집
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    • 2008.10a
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    • pp.435-438
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    • 2008
  • We demonstrated the efficient blue organic light-emitting diodes (OLEDs) by employing diarylamino-fluorene derived blue fluorescent molecules as dopants. Among those, a device exhibited blue emission with the luminous efficiency of 11.2 cd/A at $20\;mA/cm^2$, the external quantum efficiency of 9.7% at $20\;mA/cm^2$, and the $CIE_{x,y}$ coordinates of (x=0.163, y=0.259) at 8V.

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Efficient White Organic Electroluminescent Devices Consisting of Two Emitting Layers of Blue and Orange Colors

  • Lee, Nam-Heon;Lee, Mun-Jae;Song, Jun-Ho;Lee, Chang-Hee;Kwon, Soon-Ki
    • 한국정보디스플레이학회:학술대회논문집
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    • 2003.07a
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    • pp.944-947
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    • 2003
  • We report efficient white organic electroluminescent devices consisting of a blue-emitting layer of 9,10-bis[(2",7"-di-t-butyl)-9',9"-spirobifluorenyl]anthracene (TBSA) and a red-emitting layer of 4-dicyanomethylene-2-methyl-6-[2-(2,3,6,7-tetrahydro-1H,5H-benzo[i,j]quinolizin-8-yl)vinyl]-4H-pyran) (DCM2) doped into 4,4'bis[N-(1-napthyl)-N-phenyl-amino]-biphenyl (${\alpha}-NPD$). The device shows the CIE coordinates of (0.32, 0.37). The external quantum efficiency is about 3.4 % and the luminous efficiency is about 3.9 lm/W at luminance of 100 $cd/m^{2}$. The maximum luminance is about 45,400 $cd/m^{2}$ at 11.5 V.

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Efficient Deep-Blue Organic Light-emitting Diodes with Double-Emission Layers

  • Seo, Ji-Hoon;Park, Jung-Sun;Seo, Bo-Min;Lee, Kum-Hee;Park, Jung-Keun;Yoon, Seung-Soo;Kim, Young-Kwan
    • Journal of Information Display
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    • v.10 no.3
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    • pp.107-110
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    • 2009
  • Efficient deep-blue organic light-emitting diodes were demonstrated using 4,4'-bis(9-ethyl-3-carbazovinylene)-1,1'-biphenyl doped in double-emission layers (D-EMLs). The D-EML system, which consists of 2-methyl-9,10-di(2-naphthyl)anthracene and 1,4-(dinaphthalen-2-yl)-naphthalene as blue hosts, was employed to broaden the recombination zone and to ensure the good confinement of the holes and electrons. The optimized device showed a peak current efficiency of 4.47 cd/A, a peak external quantum efficiency of 4.09%, and Commission Internationale de L'Eclairage coordinates of (0.16, 0.10).

Device characteristics of blue phosphorescent organic light-emitting diodes depending on the electron transport materials

  • Lee, Hyun-Koo;Ahn, Hyuk;Lee, Chang-Hee
    • Journal of Information Display
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    • v.12 no.4
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    • pp.219-222
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    • 2011
  • Iridium-(III)-bis[(4,6-di-fluorophenyl)-pyridinate-N,$C^2$' ]picolinate-based blue phosphorescent organic light-emitting diodes with different electron transport materials were fabricated. Each electron transport material had different electron mobilities and triplet energies. The device with 1,3,5-tri(m-pyrid-3-yl-phenyl)benzene had the highest external quantum efficiency (20.1%) and luminous current efficiency (33.1 cd/A) due to its high electron mobility and triplet energy. The operational stability of each device was also compared with that of the others. The device with 2,2',2"(1,3,5-benzenetriyl)tris-(1-phenyl-1H-benzimidazole) was found to have a longer lifetime than the other devices.