한국광학회지 (Korean Journal of Optics and Photonics)

  • 제25권4호
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  • Pages.193-199
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  • 2014
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  • 1225-6285(pISSN)
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  • 2287-321X(eISSN)
한국광학회 (Optical Society of Korea)
권호 표지
DOI QR코드

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쌍극자 광원의 진동방향, Mie 산란자, 그리고 Pillow 렌즈가 OLED의 광추출효율에 미치는 영향에 대한 시뮬레이션 연구

Simulation of the Combined Effects of Dipole Emitter Orientation, Mie Scatterers, and Pillow Lenses on the Outcoupling Efficiency of an OLED

  • 이주섭 (한림대학교 전자물리학과) ;
  • 이종완 (한림대학교 전자물리학과) ;
  • 박재훈 (한림대학교 전자공학과) ;
  • 고재현 (한림대학교 전자물리학과)
  • 투고 : 2014.06.19
  • 심사 : 2014.07.17
  • 발행 : 2014.08.25
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초록

본 연구에서는 FDTD와 광선추적기법을 결합한 시뮬레이션을 활용해 광원으로 설정된 쌍극자의 진동 방향, 유리기판에 적용된 Mie 산란입자와 Pillow 렌즈가 광결정 구조가 포함된 OLED의 광추출효율에 미치는 영향을 조사하였다. 쌍극자 광원의 진동방향이 OLED 표면에 대해 수평인 경우, 광결정구조만 적용된 OLED의 효율이 54%인데 반해 최적화된 조건의 Mie 산란입자, Pillow 렌즈가 적용된 OLED는 약 86%의 광추출효율을 나타냈다. 아울러 광결정 구조로 인해 특정 각도로 광도가 증가하는 문제점이 Mie 산란입자의 산란효과로 인해 완화될 수 있음을 알았다. 본 연구는 광추출효율을 향상시키는 다양한 광학구조를 적용함과 더불어 발광체 유기분자의 배향을 조절함으로써 OLED의 효율을 큰 폭으로 향상시킬 수 있음을 보여준다.

The net effect of the emitter orientation, Mie scatters, and pillow lenses on the outcoupling efficiency (OCE) of a bottom-emitting OLED having an internal photonic crystal layer was investigated by a combined optical simulation based on the finite-difference time-domain method (FDTD) and the ray-tracing technique. The simulation showed that when the emitter orientation was horizontal with respect to the OLED surface, the OCE could be increased by 54% when a photonic crystal layer was employed, while it could be improved by 86% under optimized conditions of Mie scatters and pillow lenses applied to the glass substrate. The peculiar intensity distribution of the OLED, caused by the periodic lattice structure of the photonic crystal layer, could be ameliorated by inserting Mie scatters into the glass substrate. This study suggests that conventional outcoupling structures combined with control of the emitter orientation could improve the OCE substantially.

키워드

참고문헌

  1. K. Hong and J.-L. Lee, "Recent developments in light extraction technologies of organic light emitting diodes," Electron. Mater. Lett. 7, 77-91 (2011). https://doi.org/10.1007/s13391-011-0601-1
  2. W. Brutting, J. Frischeisen, T. D. Schmidt, B. J. Scholz, and C. Mayr, "Device efficiency of organic light-emitting diodes: Progress by improved light outcoupling," Phys. Status Solidi A 210, 44-65 (2012).
  3. G. Gu, D. Z. Garbuzov, P. E. Burrows, S. Venkatesh, and S. R. Forrest, "High-external-quantum-efficiency organic light-emitting devices," Opt. Lett. 22, 396-398 (1997). https://doi.org/10.1364/OL.22.000396
  4. J. Frischeisen, B. Scholz, B. Arndt, T. Schmidt, R. Gehlhaar, C. Adachi, and W. Brutting, "Strategies for enhanced light extraction from surface plasmons in organic light-emitting diodes," J. Photonic. Energy 1, 011004 (2011). https://doi.org/10.1117/1.3523314
  5. C. F. Madigan, M.-H. Lu, and J. C. Sturm, "Improvement of output coupling efficiency of organic light-emitting diodes by backside substrate modification," Appl. Phys. Lett. 76, 1650-1652 (2000). https://doi.org/10.1063/1.126124
  6. S. Moller and S. R. Forrest, "Improved light out-coupling in organic light emitting diodes employing ordered microlens arrays," J. Appl. Phys. 91, 3324-3327 (2002). https://doi.org/10.1063/1.1435422
  7. M.-L. Chen, A.-C. Wei, and H.-P. Shieh, "Increased organic light-emitting diode panel light efficiency by optimizing structure and improving alignment of pyramidal array lightenhancing layers," Jpn. J. Appl. Phys. 46, 1521-1525 (2007). https://doi.org/10.1143/JJAP.46.1521
  8. C.-J. Yang, S.-H. Liu, H.-H. Hsieh, C.-C. Liu, T.-Y. Cho, and C.-C. Wu, "Microcavity top-emitting organic light-emitting devices integrated with microlens arrays: Simultaneous enhancement of quantum efficiency, cd/A efficiency, color performances, and image resolution," Appl. Phys. Lett. 91, 253508 (2007). https://doi.org/10.1063/1.2827182
  9. Y.-H. Cheng, J.-L. Wu, C.-H. Cheng, K.-C. Syao, and M.-C. M. Lee, "Enhanced light outcoupling in a thin film by texturing meshed surfaces," Appl. Phys. Lett. 90, 091102 (2007). https://doi.org/10.1063/1.2709920
  10. C.-C. Liu, S.-H. Liu, K.-C. Tien, M.-H. Hsu, H.-W. Chang, C.-K. Chang, C.-J. Yang, and C.-C. Wu, "Microcavity top-emitting organic light-emitting devices integrated with diffusers for simultaneous enhancement of efficiencies and viewing characteristics," Appl. Phys. Lett. 94, 103302 (2009). https://doi.org/10.1063/1.3097354
  11. N. Nakamura, N. Fukumoto, F. Sinapi, N. Wada, Y. Aoki, and K. Maeda, "Glass substrates for OLED lighting with high out-coupling efficiency," SID'09 Tech. Digest, 603-606 (2009).
  12. S. S. Jeong and J.-H. Ko, "Simulation study on the optical structures for improving outcoupling efficiency of organic light emitting diodes," J. Inf. Disp. 13, 139-143 (2012). https://doi.org/10.1080/15980316.2012.734258
  13. S. Okutani, N. Kamiura, H. Sano, T. Sawatani, D. Fujita, T. Takehara, K. Sunohara, and M. Kobayashi, "A 20.8-inch WXGA full color AMOLED display by integrating scattering reflector with micro-bumps," SID'07 Tech. Digest, 173-176 (2007).
  14. Y. Sun and S. R. Forrest, "Enhanced light out-coupling of organic light-emitting devices using embedded low-index grids," Nature Photonics 2, 483-487 (2008). https://doi.org/10.1038/nphoton.2008.132
  15. T.-W. Koh, J.-M. Choi, S. Lee, and S. Yoo, "Optical outcoupling enhancement in organic light-emitting diodes: Highly conductive polymer as a low-index layer on microstructured ITO electrodes," Adv. Mater. 22, 1849-1853 (2010). https://doi.org/10.1002/adma.200903375
  16. W. H. Koo, S. M. Jeong, F. Araoka, K. Ishikawa, S. Nishimura, T. Toyooka, and H. Takezoe, "Light extraction from organic light-emitting diodes enhanced by spontaneously formed buckles," Nature Photonics 4, 222-226 (2010). https://doi.org/10.1038/nphoton.2010.7
  17. Y.-J. Lee, S.-H. Kim, J. Huh, G.-H. Kim, Y.-H. Lee, S.-H. Cho, Y.-C. Kim. and Y. R. Do, "A high-extraction-efficiency nanopatterned organic light-emitting diode," Appl. Phys. Lett. 82, 3779-3781 (2003). https://doi.org/10.1063/1.1577823
  18. T. Tsutsui, M. Yahiro, H. Yokogawa, K. Kawano, and M. Yokoyama, "Doubling coupling-out efficiency in organic light-emitting devices using a thin silica aerogel layer," Adv. Mater. 13, 1149-1152 (2001). https://doi.org/10.1002/1521-4095(200108)13:15<1149::AID-ADMA1149>3.0.CO;2-2
  19. H. J. Peng, Y. L. Ho, X. J. Yu, and H. S. Kwok, "Enhanced coupling of light from organic light emitting diodes using nanoporous films," J. Appl. Phys. 96, 1649-1654 (2004). https://doi.org/10.1063/1.1765859
  20. K. Hong, H. K. Yu, I. Lee, K. Kim, S. Kim, and J.-L. Lee, "Enhanced light out-coupling of organic light-emitting diodes: Spontaneously formed nanofacet-structured MgO as a refractive index modulation layer," Adv. Mater. 22, 4890-4894 (2010). https://doi.org/10.1002/adma.201002028
  21. J.-B. Kim, J.-H. Lee, C.-K. Moon, S.-Y. Kim, and J.-H. Kim, "Highly enhanced light extraction from surface plasmonic loss minimized organic light-emitting diodes," Adv. Mater. 25, 3571-3577 (2013). https://doi.org/10.1002/adma.201205233
  22. J.-H. Jang, K.-J. Kim, J.-H. Kim, and M.-C. Oh, "Outcoupling enhancement of OLED using microlens array and diffractive grating," Korean J. Opt. Photon. (Hankook Kwanghak Hoeji) 18, 441-446 (2007). https://doi.org/10.3807/HKH.2007.18.6.441
  23. S. Reineke, F. Lindner, G. Schwartz, N. Seidler, K. Walzer, B. Lussem, and K. Leo, "White organic light-emitting diodes with fluorescent tube efficiency," Nature (London) 459, 234-239 (2009). https://doi.org/10.1038/nature08003
  24. J.-S. Kim, P. K. H. Ho, N. C. Greenham, and R. H. Friend, "Electroluminescence emission pattern of organic lightemitting diodes: Implications for device efficiency calculations," J. Appl. Phys. 88, 1073-1081 (2000). https://doi.org/10.1063/1.373779
  25. M. Flammich, M. C. Gather, N. Danz, D. Michaelis, A. H. Brauer, K. Meerholz, and A. Tunnermann, "Orientation of emissive dipole in OLEDs: Quantitative in situ analysis," Org. Electron. 11, 1039-1046 (2010). https://doi.org/10.1016/j.orgel.2010.03.002
  26. M. Flammich, J. Frischeisen, D. S. Setz, D. Michaelis, B. C. Krummacher, T. D. Schmidt, W. Brutting, and N. Danz, "Oriented phosphorescent emitters boost OLED efficiency," Org. Electron. 12, 1663-1668 (2011). https://doi.org/10.1016/j.orgel.2011.06.011
  27. P. Liehm, C. Murawski, M. Furno, B. Lussem, K. Leo, and M. C. Gather, "Comparing the emissive dipole orientation of two similar phosphorescent green emitter molecules in highly efficient organic light-emitting diodes," Appl. Phys. Lett. 101, 253304 (2012). https://doi.org/10.1063/1.4773188
  28. S.-Y. Kim, W.-I. Jeong, C. Mayr, Y.-S. Park, K.-H. Kim, J.-H. Lee, C.-K. Moon, W. Brutting, and J.-J. Kim, "Organic light-emitting diodes with 30% external quantum effi ciency based on a horizontally oriented emitter," Adv. Funct. Mater. 23, 3896-3900 (2013). https://doi.org/10.1002/adfm.201300104
  29. K.-H. Kim, C.-K. Moon, J.-H. Lee, S.-Y. Kim, and J.-J. Kim, "Highly efficient organic light-emitting diodes with phosphorescent emitters having high quantum yield and horizontal orientation of transition dipole moments," Adv. Mater. DOI: 10.1002/adma.201305733 (2014).
  30. J. S. Lee, J.-H. Ko, J. Park, and J. W. Lee, "Simulation study on the effect of the emitter orientation and photonic crystals on the outcoupling efficiency of organic lightemitting diodes," submitted to J. Opt. Soc. Korea.
  31. S. S. Jeong and J.-H. Ko, "Optical simulation study on the effect of diffusing substrate and pillow lenses on the outcoupling efficiency of organic light emitting diodes," J. Opt. Soc. Korea 17, 269-274 (2013). https://doi.org/10.3807/JOSK.2013.17.3.269
  32. S. S. Jeong, H.-W. Choi, and J.-H. Ko, "Simulation study on the outcoupling efficiency and intensity distribution of photonic crystal-based organic light-emitting diodes," New Physics: Sae Mulli 63, 892-899 (2013). https://doi.org/10.3938/NPSM.63.892