Abstract

In this paper, we experimentally and theoretically investigated the optical characteristics of organic light-emitting devices (OLEDs), having different pixel sizes and attached with patterned microlens array films. For a regular microlens array, though it can extract the waveguiding light and increase luminous current efficiency for a large-pixelated OLED, we observed that it decreases the luminance to an even lower level than that of the planar OLED as its pixel size is close to the microlens dimension. Although a microlens can effectively outcouple the light rays originally at incident angles larger than the critical angle, it also can impede the outcoupling for the light rays originally at incident angles smaller than the critical angle. Enhancement or reduction of the light extraction depends on the relative positions of the light emitting point and the microlens. Therefore, we proposed a center-hollowed microlens array, of which the microlenses directly upon the pixel are removed, and proved that it can increase the luminous current efficiency and luminous power efficiency of a small-pixelated OLED. By attaching this patterned microlens array, 87% of luminance enhancement in the normal direction was observed for a 0.1×0.1 mm2 OLED pixel. On the other hand, a regular microlens array resulted in 4% decrease under the same condition.

© 2008 Optical Society of America

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  1. M.-H. Lu and J. C. Sturm, "Optimization of external coupling and light emission in organic light-emitting devices: modeling and experiment," J. Appl. Phys. 91, 595-604 (2002).
    [CrossRef]
  2. S. Möller and S. R. Forrest, "Improved light out-coupling in organic light-emitting diodes employing ordered microlens arrays," J. Appl. Phys. 91, 3324-3327 (2002).
    [CrossRef]
  3. M.-K. Wei and I-L. Su, "Method to evaluate the enhancement of luminance efficiency in planar OLED light emitting devices for microlens array," Opt. Express 12, 5777-5782 (2004).
    [CrossRef] [PubMed]
  4. H. Peng, Y. L. Ho, X.-J. Yu, M. Wong, and H.-S. Kwok, "Coupling efficiency enhancement in organic light-emitting devices using microlens array-theory and experiment," J. Display Technol. 1, 278-282 (2005).
    [CrossRef]
  5. J. Lim, S. S. Oh, D. Y. Kim, S. J. Cho, I. T. Kim, S. H. Han, H. Takezoe, E. H. Choi, G. S. Cho, S. O. Kang, and B. Park, "Enhanced out-coupling factor of microcavity organic light-emitting devices with irregular microlens array," Opt. Express 14, 6564-6571 (2006).
    [CrossRef] [PubMed]
  6. Y. Sun and S. R. Forrest, "Organic light emitting devices with enhanced outcoupling via microlenses fabricated by imprint lithography," J. Appl. Phys. 100, 073106 (2006).
    [CrossRef]
  7. M.-K. Wei, I-L. Su, Y.-J. Chen, M. Chang, H.-Y. Ling, and T.-C. Wu, "The influence of a microlens array on planar organic light-emitting devices," J. Micromech. Microeng. 16, 368-374 (2006).
    [CrossRef]
  8. H. Greiner, "Light extraction from organic light emitting diode substrates: simulation and experiment," Jpn. J. Appl. Phys. 46, 4125-4137 (2007).
    [CrossRef]
  9. 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).
    [CrossRef]
  10. T. Nakamura, N. Tsutsumi, N. Juni, and H. Fuji, "Thin-film waveguiding mode light extraction in organic electroluminescent device using high refractive index substrate," J. Appl. Phys. 97, 054505 (2005).
    [CrossRef]
  11. M.-K. Wei, J.-H. Lee, H.-Y. Lin, Y.-H. Ho, K.-Y. Chen, C.-C. Lin, C.-F. Wu, H.-Y. Lin, J.-H. Tsai, and T.-C. Wu, "Efficiency improvement and spectral shift of an organic light-emitting device by attaching a hexagon-based microlens array," J. Opt. A: Pure Appl. Opt. 10, 055302 (2008).
    [CrossRef]
  12. B. C. Krummacher, M. K. Mathai, V. Choong, S. A. Choulis, F. So, and A. Winnacker, "General method to evaluate substrate surface modification techniques for light extraction enhancement of organic light emitting diodes," J. Appl. Phys. 100, 054702 (2006).
    [CrossRef]
  13. H.-Y. Lin, J.-H. Lee, M.-K. Wei, C.-L. Dai, C.-F. Wu, Y.-H. Ho, H.-Y. Lin, and T.-C. Wu, "Improvement of the outcoupling efficiency of an organic light-emitting device by attaching microstructured films," Opt. Commun. 275, 464-9 (2007).
    [CrossRef]
  14. C.-H. Hsiao, C.-F. Lin, and J.-H. Lee, "Driving voltage reduction in white organic light-emitting devices from selectively doping in ambipolar blue emitting layer," J. Appl. Phys. 102, 094508 (2007).
    [CrossRef]
  15. C. Y. Lin, S. C. Hsu, K. Y. Chen, H. Y. Lin, J. H. Lee, and M. K. Wei, "Low blur effect and high light extraction efficiency enhancement of organic light emitting displays with novel microstructure attachment," Soc. Inf. Display Tech. Digest 38, 867-870 (2007).
    [CrossRef]

2008 (1)

M.-K. Wei, J.-H. Lee, H.-Y. Lin, Y.-H. Ho, K.-Y. Chen, C.-C. Lin, C.-F. Wu, H.-Y. Lin, J.-H. Tsai, and T.-C. Wu, "Efficiency improvement and spectral shift of an organic light-emitting device by attaching a hexagon-based microlens array," J. Opt. A: Pure Appl. Opt. 10, 055302 (2008).
[CrossRef]

2007 (5)

H.-Y. Lin, J.-H. Lee, M.-K. Wei, C.-L. Dai, C.-F. Wu, Y.-H. Ho, H.-Y. Lin, and T.-C. Wu, "Improvement of the outcoupling efficiency of an organic light-emitting device by attaching microstructured films," Opt. Commun. 275, 464-9 (2007).
[CrossRef]

C.-H. Hsiao, C.-F. Lin, and J.-H. Lee, "Driving voltage reduction in white organic light-emitting devices from selectively doping in ambipolar blue emitting layer," J. Appl. Phys. 102, 094508 (2007).
[CrossRef]

C. Y. Lin, S. C. Hsu, K. Y. Chen, H. Y. Lin, J. H. Lee, and M. K. Wei, "Low blur effect and high light extraction efficiency enhancement of organic light emitting displays with novel microstructure attachment," Soc. Inf. Display Tech. Digest 38, 867-870 (2007).
[CrossRef]

H. Greiner, "Light extraction from organic light emitting diode substrates: simulation and experiment," Jpn. J. Appl. Phys. 46, 4125-4137 (2007).
[CrossRef]

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).
[CrossRef]

2006 (4)

J. Lim, S. S. Oh, D. Y. Kim, S. J. Cho, I. T. Kim, S. H. Han, H. Takezoe, E. H. Choi, G. S. Cho, S. O. Kang, and B. Park, "Enhanced out-coupling factor of microcavity organic light-emitting devices with irregular microlens array," Opt. Express 14, 6564-6571 (2006).
[CrossRef] [PubMed]

Y. Sun and S. R. Forrest, "Organic light emitting devices with enhanced outcoupling via microlenses fabricated by imprint lithography," J. Appl. Phys. 100, 073106 (2006).
[CrossRef]

M.-K. Wei, I-L. Su, Y.-J. Chen, M. Chang, H.-Y. Ling, and T.-C. Wu, "The influence of a microlens array on planar organic light-emitting devices," J. Micromech. Microeng. 16, 368-374 (2006).
[CrossRef]

B. C. Krummacher, M. K. Mathai, V. Choong, S. A. Choulis, F. So, and A. Winnacker, "General method to evaluate substrate surface modification techniques for light extraction enhancement of organic light emitting diodes," J. Appl. Phys. 100, 054702 (2006).
[CrossRef]

2005 (2)

T. Nakamura, N. Tsutsumi, N. Juni, and H. Fuji, "Thin-film waveguiding mode light extraction in organic electroluminescent device using high refractive index substrate," J. Appl. Phys. 97, 054505 (2005).
[CrossRef]

H. Peng, Y. L. Ho, X.-J. Yu, M. Wong, and H.-S. Kwok, "Coupling efficiency enhancement in organic light-emitting devices using microlens array-theory and experiment," J. Display Technol. 1, 278-282 (2005).
[CrossRef]

2004 (1)

M.-K. Wei and I-L. Su, "Method to evaluate the enhancement of luminance efficiency in planar OLED light emitting devices for microlens array," Opt. Express 12, 5777-5782 (2004).
[CrossRef] [PubMed]

2002 (2)

M.-H. Lu and J. C. Sturm, "Optimization of external coupling and light emission in organic light-emitting devices: modeling and experiment," J. Appl. Phys. 91, 595-604 (2002).
[CrossRef]

S. Möller and S. R. Forrest, "Improved light out-coupling in organic light-emitting diodes employing ordered microlens arrays," J. Appl. Phys. 91, 3324-3327 (2002).
[CrossRef]

Chang, M.

M.-K. Wei, I-L. Su, Y.-J. Chen, M. Chang, H.-Y. Ling, and T.-C. Wu, "The influence of a microlens array on planar organic light-emitting devices," J. Micromech. Microeng. 16, 368-374 (2006).
[CrossRef]

Chen, K. Y.

C. Y. Lin, S. C. Hsu, K. Y. Chen, H. Y. Lin, J. H. Lee, and M. K. Wei, "Low blur effect and high light extraction efficiency enhancement of organic light emitting displays with novel microstructure attachment," Soc. Inf. Display Tech. Digest 38, 867-870 (2007).
[CrossRef]

Chen, K.-Y.

M.-K. Wei, J.-H. Lee, H.-Y. Lin, Y.-H. Ho, K.-Y. Chen, C.-C. Lin, C.-F. Wu, H.-Y. Lin, J.-H. Tsai, and T.-C. Wu, "Efficiency improvement and spectral shift of an organic light-emitting device by attaching a hexagon-based microlens array," J. Opt. A: Pure Appl. Opt. 10, 055302 (2008).
[CrossRef]

Chen, Y.-J.

M.-K. Wei, I-L. Su, Y.-J. Chen, M. Chang, H.-Y. Ling, and T.-C. Wu, "The influence of a microlens array on planar organic light-emitting devices," J. Micromech. Microeng. 16, 368-374 (2006).
[CrossRef]

Cho, G. S.

J. Lim, S. S. Oh, D. Y. Kim, S. J. Cho, I. T. Kim, S. H. Han, H. Takezoe, E. H. Choi, G. S. Cho, S. O. Kang, and B. Park, "Enhanced out-coupling factor of microcavity organic light-emitting devices with irregular microlens array," Opt. Express 14, 6564-6571 (2006).
[CrossRef] [PubMed]

Cho, S. J.

J. Lim, S. S. Oh, D. Y. Kim, S. J. Cho, I. T. Kim, S. H. Han, H. Takezoe, E. H. Choi, G. S. Cho, S. O. Kang, and B. Park, "Enhanced out-coupling factor of microcavity organic light-emitting devices with irregular microlens array," Opt. Express 14, 6564-6571 (2006).
[CrossRef] [PubMed]

Cho, T.-Y.

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).
[CrossRef]

Choi, E. H.

J. Lim, S. S. Oh, D. Y. Kim, S. J. Cho, I. T. Kim, S. H. Han, H. Takezoe, E. H. Choi, G. S. Cho, S. O. Kang, and B. Park, "Enhanced out-coupling factor of microcavity organic light-emitting devices with irregular microlens array," Opt. Express 14, 6564-6571 (2006).
[CrossRef] [PubMed]

Choong, V.

B. C. Krummacher, M. K. Mathai, V. Choong, S. A. Choulis, F. So, and A. Winnacker, "General method to evaluate substrate surface modification techniques for light extraction enhancement of organic light emitting diodes," J. Appl. Phys. 100, 054702 (2006).
[CrossRef]

Choulis, S. A.

B. C. Krummacher, M. K. Mathai, V. Choong, S. A. Choulis, F. So, and A. Winnacker, "General method to evaluate substrate surface modification techniques for light extraction enhancement of organic light emitting diodes," J. Appl. Phys. 100, 054702 (2006).
[CrossRef]

Dai, C.-L.

H.-Y. Lin, J.-H. Lee, M.-K. Wei, C.-L. Dai, C.-F. Wu, Y.-H. Ho, H.-Y. Lin, and T.-C. Wu, "Improvement of the outcoupling efficiency of an organic light-emitting device by attaching microstructured films," Opt. Commun. 275, 464-9 (2007).
[CrossRef]

Forrest, S. R.

Y. Sun and S. R. Forrest, "Organic light emitting devices with enhanced outcoupling via microlenses fabricated by imprint lithography," J. Appl. Phys. 100, 073106 (2006).
[CrossRef]

S. Möller and S. R. Forrest, "Improved light out-coupling in organic light-emitting diodes employing ordered microlens arrays," J. Appl. Phys. 91, 3324-3327 (2002).
[CrossRef]

Fuji, H.

T. Nakamura, N. Tsutsumi, N. Juni, and H. Fuji, "Thin-film waveguiding mode light extraction in organic electroluminescent device using high refractive index substrate," J. Appl. Phys. 97, 054505 (2005).
[CrossRef]

Greiner, H.

H. Greiner, "Light extraction from organic light emitting diode substrates: simulation and experiment," Jpn. J. Appl. Phys. 46, 4125-4137 (2007).
[CrossRef]

Han, S. H.

J. Lim, S. S. Oh, D. Y. Kim, S. J. Cho, I. T. Kim, S. H. Han, H. Takezoe, E. H. Choi, G. S. Cho, S. O. Kang, and B. Park, "Enhanced out-coupling factor of microcavity organic light-emitting devices with irregular microlens array," Opt. Express 14, 6564-6571 (2006).
[CrossRef] [PubMed]

Ho, Y. L.

H. Peng, Y. L. Ho, X.-J. Yu, M. Wong, and H.-S. Kwok, "Coupling efficiency enhancement in organic light-emitting devices using microlens array-theory and experiment," J. Display Technol. 1, 278-282 (2005).
[CrossRef]

Ho, Y.-H.

M.-K. Wei, J.-H. Lee, H.-Y. Lin, Y.-H. Ho, K.-Y. Chen, C.-C. Lin, C.-F. Wu, H.-Y. Lin, J.-H. Tsai, and T.-C. Wu, "Efficiency improvement and spectral shift of an organic light-emitting device by attaching a hexagon-based microlens array," J. Opt. A: Pure Appl. Opt. 10, 055302 (2008).
[CrossRef]

H.-Y. Lin, J.-H. Lee, M.-K. Wei, C.-L. Dai, C.-F. Wu, Y.-H. Ho, H.-Y. Lin, and T.-C. Wu, "Improvement of the outcoupling efficiency of an organic light-emitting device by attaching microstructured films," Opt. Commun. 275, 464-9 (2007).
[CrossRef]

Hsiao, C.-H.

C.-H. Hsiao, C.-F. Lin, and J.-H. Lee, "Driving voltage reduction in white organic light-emitting devices from selectively doping in ambipolar blue emitting layer," J. Appl. Phys. 102, 094508 (2007).
[CrossRef]

Hsieh, H.-H.

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).
[CrossRef]

Hsu, S. C.

C. Y. Lin, S. C. Hsu, K. Y. Chen, H. Y. Lin, J. H. Lee, and M. K. Wei, "Low blur effect and high light extraction efficiency enhancement of organic light emitting displays with novel microstructure attachment," Soc. Inf. Display Tech. Digest 38, 867-870 (2007).
[CrossRef]

Juni, N.

T. Nakamura, N. Tsutsumi, N. Juni, and H. Fuji, "Thin-film waveguiding mode light extraction in organic electroluminescent device using high refractive index substrate," J. Appl. Phys. 97, 054505 (2005).
[CrossRef]

Kang, S. O.

J. Lim, S. S. Oh, D. Y. Kim, S. J. Cho, I. T. Kim, S. H. Han, H. Takezoe, E. H. Choi, G. S. Cho, S. O. Kang, and B. Park, "Enhanced out-coupling factor of microcavity organic light-emitting devices with irregular microlens array," Opt. Express 14, 6564-6571 (2006).
[CrossRef] [PubMed]

Kim, D. Y.

J. Lim, S. S. Oh, D. Y. Kim, S. J. Cho, I. T. Kim, S. H. Han, H. Takezoe, E. H. Choi, G. S. Cho, S. O. Kang, and B. Park, "Enhanced out-coupling factor of microcavity organic light-emitting devices with irregular microlens array," Opt. Express 14, 6564-6571 (2006).
[CrossRef] [PubMed]

Kim, I. T.

J. Lim, S. S. Oh, D. Y. Kim, S. J. Cho, I. T. Kim, S. H. Han, H. Takezoe, E. H. Choi, G. S. Cho, S. O. Kang, and B. Park, "Enhanced out-coupling factor of microcavity organic light-emitting devices with irregular microlens array," Opt. Express 14, 6564-6571 (2006).
[CrossRef] [PubMed]

Krummacher, B. C.

B. C. Krummacher, M. K. Mathai, V. Choong, S. A. Choulis, F. So, and A. Winnacker, "General method to evaluate substrate surface modification techniques for light extraction enhancement of organic light emitting diodes," J. Appl. Phys. 100, 054702 (2006).
[CrossRef]

Kwok, H.-S.

H. Peng, Y. L. Ho, X.-J. Yu, M. Wong, and H.-S. Kwok, "Coupling efficiency enhancement in organic light-emitting devices using microlens array-theory and experiment," J. Display Technol. 1, 278-282 (2005).
[CrossRef]

Lee, J. H.

C. Y. Lin, S. C. Hsu, K. Y. Chen, H. Y. Lin, J. H. Lee, and M. K. Wei, "Low blur effect and high light extraction efficiency enhancement of organic light emitting displays with novel microstructure attachment," Soc. Inf. Display Tech. Digest 38, 867-870 (2007).
[CrossRef]

Lee, J.-H.

M.-K. Wei, J.-H. Lee, H.-Y. Lin, Y.-H. Ho, K.-Y. Chen, C.-C. Lin, C.-F. Wu, H.-Y. Lin, J.-H. Tsai, and T.-C. Wu, "Efficiency improvement and spectral shift of an organic light-emitting device by attaching a hexagon-based microlens array," J. Opt. A: Pure Appl. Opt. 10, 055302 (2008).
[CrossRef]

C.-H. Hsiao, C.-F. Lin, and J.-H. Lee, "Driving voltage reduction in white organic light-emitting devices from selectively doping in ambipolar blue emitting layer," J. Appl. Phys. 102, 094508 (2007).
[CrossRef]

H.-Y. Lin, J.-H. Lee, M.-K. Wei, C.-L. Dai, C.-F. Wu, Y.-H. Ho, H.-Y. Lin, and T.-C. Wu, "Improvement of the outcoupling efficiency of an organic light-emitting device by attaching microstructured films," Opt. Commun. 275, 464-9 (2007).
[CrossRef]

Lim, J.

J. Lim, S. S. Oh, D. Y. Kim, S. J. Cho, I. T. Kim, S. H. Han, H. Takezoe, E. H. Choi, G. S. Cho, S. O. Kang, and B. Park, "Enhanced out-coupling factor of microcavity organic light-emitting devices with irregular microlens array," Opt. Express 14, 6564-6571 (2006).
[CrossRef] [PubMed]

Lin, C. Y.

C. Y. Lin, S. C. Hsu, K. Y. Chen, H. Y. Lin, J. H. Lee, and M. K. Wei, "Low blur effect and high light extraction efficiency enhancement of organic light emitting displays with novel microstructure attachment," Soc. Inf. Display Tech. Digest 38, 867-870 (2007).
[CrossRef]

Lin, C.-C.

M.-K. Wei, J.-H. Lee, H.-Y. Lin, Y.-H. Ho, K.-Y. Chen, C.-C. Lin, C.-F. Wu, H.-Y. Lin, J.-H. Tsai, and T.-C. Wu, "Efficiency improvement and spectral shift of an organic light-emitting device by attaching a hexagon-based microlens array," J. Opt. A: Pure Appl. Opt. 10, 055302 (2008).
[CrossRef]

Lin, C.-F.

C.-H. Hsiao, C.-F. Lin, and J.-H. Lee, "Driving voltage reduction in white organic light-emitting devices from selectively doping in ambipolar blue emitting layer," J. Appl. Phys. 102, 094508 (2007).
[CrossRef]

Lin, H. Y.

C. Y. Lin, S. C. Hsu, K. Y. Chen, H. Y. Lin, J. H. Lee, and M. K. Wei, "Low blur effect and high light extraction efficiency enhancement of organic light emitting displays with novel microstructure attachment," Soc. Inf. Display Tech. Digest 38, 867-870 (2007).
[CrossRef]

Lin, H.-Y.

M.-K. Wei, J.-H. Lee, H.-Y. Lin, Y.-H. Ho, K.-Y. Chen, C.-C. Lin, C.-F. Wu, H.-Y. Lin, J.-H. Tsai, and T.-C. Wu, "Efficiency improvement and spectral shift of an organic light-emitting device by attaching a hexagon-based microlens array," J. Opt. A: Pure Appl. Opt. 10, 055302 (2008).
[CrossRef]

M.-K. Wei, J.-H. Lee, H.-Y. Lin, Y.-H. Ho, K.-Y. Chen, C.-C. Lin, C.-F. Wu, H.-Y. Lin, J.-H. Tsai, and T.-C. Wu, "Efficiency improvement and spectral shift of an organic light-emitting device by attaching a hexagon-based microlens array," J. Opt. A: Pure Appl. Opt. 10, 055302 (2008).
[CrossRef]

H.-Y. Lin, J.-H. Lee, M.-K. Wei, C.-L. Dai, C.-F. Wu, Y.-H. Ho, H.-Y. Lin, and T.-C. Wu, "Improvement of the outcoupling efficiency of an organic light-emitting device by attaching microstructured films," Opt. Commun. 275, 464-9 (2007).
[CrossRef]

H.-Y. Lin, J.-H. Lee, M.-K. Wei, C.-L. Dai, C.-F. Wu, Y.-H. Ho, H.-Y. Lin, and T.-C. Wu, "Improvement of the outcoupling efficiency of an organic light-emitting device by attaching microstructured films," Opt. Commun. 275, 464-9 (2007).
[CrossRef]

Ling, H.-Y.

M.-K. Wei, I-L. Su, Y.-J. Chen, M. Chang, H.-Y. Ling, and T.-C. Wu, "The influence of a microlens array on planar organic light-emitting devices," J. Micromech. Microeng. 16, 368-374 (2006).
[CrossRef]

Liu, C.-C.

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).
[CrossRef]

Liu, S.-H.

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).
[CrossRef]

Lu, M.-H.

M.-H. Lu and J. C. Sturm, "Optimization of external coupling and light emission in organic light-emitting devices: modeling and experiment," J. Appl. Phys. 91, 595-604 (2002).
[CrossRef]

Mathai, M. K.

B. C. Krummacher, M. K. Mathai, V. Choong, S. A. Choulis, F. So, and A. Winnacker, "General method to evaluate substrate surface modification techniques for light extraction enhancement of organic light emitting diodes," J. Appl. Phys. 100, 054702 (2006).
[CrossRef]

Möller, S.

S. Möller and S. R. Forrest, "Improved light out-coupling in organic light-emitting diodes employing ordered microlens arrays," J. Appl. Phys. 91, 3324-3327 (2002).
[CrossRef]

Nakamura, T.

T. Nakamura, N. Tsutsumi, N. Juni, and H. Fuji, "Thin-film waveguiding mode light extraction in organic electroluminescent device using high refractive index substrate," J. Appl. Phys. 97, 054505 (2005).
[CrossRef]

Oh, S. S.

J. Lim, S. S. Oh, D. Y. Kim, S. J. Cho, I. T. Kim, S. H. Han, H. Takezoe, E. H. Choi, G. S. Cho, S. O. Kang, and B. Park, "Enhanced out-coupling factor of microcavity organic light-emitting devices with irregular microlens array," Opt. Express 14, 6564-6571 (2006).
[CrossRef] [PubMed]

Park, B.

J. Lim, S. S. Oh, D. Y. Kim, S. J. Cho, I. T. Kim, S. H. Han, H. Takezoe, E. H. Choi, G. S. Cho, S. O. Kang, and B. Park, "Enhanced out-coupling factor of microcavity organic light-emitting devices with irregular microlens array," Opt. Express 14, 6564-6571 (2006).
[CrossRef] [PubMed]

Peng, H.

H. Peng, Y. L. Ho, X.-J. Yu, M. Wong, and H.-S. Kwok, "Coupling efficiency enhancement in organic light-emitting devices using microlens array-theory and experiment," J. Display Technol. 1, 278-282 (2005).
[CrossRef]

So, F.

B. C. Krummacher, M. K. Mathai, V. Choong, S. A. Choulis, F. So, and A. Winnacker, "General method to evaluate substrate surface modification techniques for light extraction enhancement of organic light emitting diodes," J. Appl. Phys. 100, 054702 (2006).
[CrossRef]

Sturm, J. C.

M.-H. Lu and J. C. Sturm, "Optimization of external coupling and light emission in organic light-emitting devices: modeling and experiment," J. Appl. Phys. 91, 595-604 (2002).
[CrossRef]

Su, I-L.

M.-K. Wei, I-L. Su, Y.-J. Chen, M. Chang, H.-Y. Ling, and T.-C. Wu, "The influence of a microlens array on planar organic light-emitting devices," J. Micromech. Microeng. 16, 368-374 (2006).
[CrossRef]

M.-K. Wei and I-L. Su, "Method to evaluate the enhancement of luminance efficiency in planar OLED light emitting devices for microlens array," Opt. Express 12, 5777-5782 (2004).
[CrossRef] [PubMed]

Sun, Y.

Y. Sun and S. R. Forrest, "Organic light emitting devices with enhanced outcoupling via microlenses fabricated by imprint lithography," J. Appl. Phys. 100, 073106 (2006).
[CrossRef]

Takezoe, H.

J. Lim, S. S. Oh, D. Y. Kim, S. J. Cho, I. T. Kim, S. H. Han, H. Takezoe, E. H. Choi, G. S. Cho, S. O. Kang, and B. Park, "Enhanced out-coupling factor of microcavity organic light-emitting devices with irregular microlens array," Opt. Express 14, 6564-6571 (2006).
[CrossRef] [PubMed]

Tsai, J.-H.

M.-K. Wei, J.-H. Lee, H.-Y. Lin, Y.-H. Ho, K.-Y. Chen, C.-C. Lin, C.-F. Wu, H.-Y. Lin, J.-H. Tsai, and T.-C. Wu, "Efficiency improvement and spectral shift of an organic light-emitting device by attaching a hexagon-based microlens array," J. Opt. A: Pure Appl. Opt. 10, 055302 (2008).
[CrossRef]

Tsutsumi, N.

T. Nakamura, N. Tsutsumi, N. Juni, and H. Fuji, "Thin-film waveguiding mode light extraction in organic electroluminescent device using high refractive index substrate," J. Appl. Phys. 97, 054505 (2005).
[CrossRef]

Wei, M. K.

C. Y. Lin, S. C. Hsu, K. Y. Chen, H. Y. Lin, J. H. Lee, and M. K. Wei, "Low blur effect and high light extraction efficiency enhancement of organic light emitting displays with novel microstructure attachment," Soc. Inf. Display Tech. Digest 38, 867-870 (2007).
[CrossRef]

Wei, M.-K.

M.-K. Wei, J.-H. Lee, H.-Y. Lin, Y.-H. Ho, K.-Y. Chen, C.-C. Lin, C.-F. Wu, H.-Y. Lin, J.-H. Tsai, and T.-C. Wu, "Efficiency improvement and spectral shift of an organic light-emitting device by attaching a hexagon-based microlens array," J. Opt. A: Pure Appl. Opt. 10, 055302 (2008).
[CrossRef]

H.-Y. Lin, J.-H. Lee, M.-K. Wei, C.-L. Dai, C.-F. Wu, Y.-H. Ho, H.-Y. Lin, and T.-C. Wu, "Improvement of the outcoupling efficiency of an organic light-emitting device by attaching microstructured films," Opt. Commun. 275, 464-9 (2007).
[CrossRef]

M.-K. Wei, I-L. Su, Y.-J. Chen, M. Chang, H.-Y. Ling, and T.-C. Wu, "The influence of a microlens array on planar organic light-emitting devices," J. Micromech. Microeng. 16, 368-374 (2006).
[CrossRef]

M.-K. Wei and I-L. Su, "Method to evaluate the enhancement of luminance efficiency in planar OLED light emitting devices for microlens array," Opt. Express 12, 5777-5782 (2004).
[CrossRef] [PubMed]

Winnacker, A.

B. C. Krummacher, M. K. Mathai, V. Choong, S. A. Choulis, F. So, and A. Winnacker, "General method to evaluate substrate surface modification techniques for light extraction enhancement of organic light emitting diodes," J. Appl. Phys. 100, 054702 (2006).
[CrossRef]

Wong, M.

H. Peng, Y. L. Ho, X.-J. Yu, M. Wong, and H.-S. Kwok, "Coupling efficiency enhancement in organic light-emitting devices using microlens array-theory and experiment," J. Display Technol. 1, 278-282 (2005).
[CrossRef]

Wu, C.-C.

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).
[CrossRef]

Wu, C.-F.

M.-K. Wei, J.-H. Lee, H.-Y. Lin, Y.-H. Ho, K.-Y. Chen, C.-C. Lin, C.-F. Wu, H.-Y. Lin, J.-H. Tsai, and T.-C. Wu, "Efficiency improvement and spectral shift of an organic light-emitting device by attaching a hexagon-based microlens array," J. Opt. A: Pure Appl. Opt. 10, 055302 (2008).
[CrossRef]

H.-Y. Lin, J.-H. Lee, M.-K. Wei, C.-L. Dai, C.-F. Wu, Y.-H. Ho, H.-Y. Lin, and T.-C. Wu, "Improvement of the outcoupling efficiency of an organic light-emitting device by attaching microstructured films," Opt. Commun. 275, 464-9 (2007).
[CrossRef]

Wu, T.-C.

M.-K. Wei, J.-H. Lee, H.-Y. Lin, Y.-H. Ho, K.-Y. Chen, C.-C. Lin, C.-F. Wu, H.-Y. Lin, J.-H. Tsai, and T.-C. Wu, "Efficiency improvement and spectral shift of an organic light-emitting device by attaching a hexagon-based microlens array," J. Opt. A: Pure Appl. Opt. 10, 055302 (2008).
[CrossRef]

H.-Y. Lin, J.-H. Lee, M.-K. Wei, C.-L. Dai, C.-F. Wu, Y.-H. Ho, H.-Y. Lin, and T.-C. Wu, "Improvement of the outcoupling efficiency of an organic light-emitting device by attaching microstructured films," Opt. Commun. 275, 464-9 (2007).
[CrossRef]

M.-K. Wei, I-L. Su, Y.-J. Chen, M. Chang, H.-Y. Ling, and T.-C. Wu, "The influence of a microlens array on planar organic light-emitting devices," J. Micromech. Microeng. 16, 368-374 (2006).
[CrossRef]

Yang, C.-J.

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).
[CrossRef]

Yu, X.-J.

H. Peng, Y. L. Ho, X.-J. Yu, M. Wong, and H.-S. Kwok, "Coupling efficiency enhancement in organic light-emitting devices using microlens array-theory and experiment," J. Display Technol. 1, 278-282 (2005).
[CrossRef]

Appl. Phys. Lett. (1)

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).
[CrossRef]

J. Appl. Phys. (6)

T. Nakamura, N. Tsutsumi, N. Juni, and H. Fuji, "Thin-film waveguiding mode light extraction in organic electroluminescent device using high refractive index substrate," J. Appl. Phys. 97, 054505 (2005).
[CrossRef]

Y. Sun and S. R. Forrest, "Organic light emitting devices with enhanced outcoupling via microlenses fabricated by imprint lithography," J. Appl. Phys. 100, 073106 (2006).
[CrossRef]

M.-H. Lu and J. C. Sturm, "Optimization of external coupling and light emission in organic light-emitting devices: modeling and experiment," J. Appl. Phys. 91, 595-604 (2002).
[CrossRef]

S. Möller and S. R. Forrest, "Improved light out-coupling in organic light-emitting diodes employing ordered microlens arrays," J. Appl. Phys. 91, 3324-3327 (2002).
[CrossRef]

B. C. Krummacher, M. K. Mathai, V. Choong, S. A. Choulis, F. So, and A. Winnacker, "General method to evaluate substrate surface modification techniques for light extraction enhancement of organic light emitting diodes," J. Appl. Phys. 100, 054702 (2006).
[CrossRef]

C.-H. Hsiao, C.-F. Lin, and J.-H. Lee, "Driving voltage reduction in white organic light-emitting devices from selectively doping in ambipolar blue emitting layer," J. Appl. Phys. 102, 094508 (2007).
[CrossRef]

J. Display Technol. (1)

H. Peng, Y. L. Ho, X.-J. Yu, M. Wong, and H.-S. Kwok, "Coupling efficiency enhancement in organic light-emitting devices using microlens array-theory and experiment," J. Display Technol. 1, 278-282 (2005).
[CrossRef]

J. Micromech. Microeng. (1)

M.-K. Wei, I-L. Su, Y.-J. Chen, M. Chang, H.-Y. Ling, and T.-C. Wu, "The influence of a microlens array on planar organic light-emitting devices," J. Micromech. Microeng. 16, 368-374 (2006).
[CrossRef]

J. Opt. A: Pure Appl. Opt. (1)

M.-K. Wei, J.-H. Lee, H.-Y. Lin, Y.-H. Ho, K.-Y. Chen, C.-C. Lin, C.-F. Wu, H.-Y. Lin, J.-H. Tsai, and T.-C. Wu, "Efficiency improvement and spectral shift of an organic light-emitting device by attaching a hexagon-based microlens array," J. Opt. A: Pure Appl. Opt. 10, 055302 (2008).
[CrossRef]

Jpn. J. Appl. Phys. (1)

H. Greiner, "Light extraction from organic light emitting diode substrates: simulation and experiment," Jpn. J. Appl. Phys. 46, 4125-4137 (2007).
[CrossRef]

Opt. Commun. (1)

H.-Y. Lin, J.-H. Lee, M.-K. Wei, C.-L. Dai, C.-F. Wu, Y.-H. Ho, H.-Y. Lin, and T.-C. Wu, "Improvement of the outcoupling efficiency of an organic light-emitting device by attaching microstructured films," Opt. Commun. 275, 464-9 (2007).
[CrossRef]

Opt. Express (2)

J. Lim, S. S. Oh, D. Y. Kim, S. J. Cho, I. T. Kim, S. H. Han, H. Takezoe, E. H. Choi, G. S. Cho, S. O. Kang, and B. Park, "Enhanced out-coupling factor of microcavity organic light-emitting devices with irregular microlens array," Opt. Express 14, 6564-6571 (2006).
[CrossRef] [PubMed]

M.-K. Wei and I-L. Su, "Method to evaluate the enhancement of luminance efficiency in planar OLED light emitting devices for microlens array," Opt. Express 12, 5777-5782 (2004).
[CrossRef] [PubMed]

Soc. Inf. Display Tech. Digest (1)

C. Y. Lin, S. C. Hsu, K. Y. Chen, H. Y. Lin, J. H. Lee, and M. K. Wei, "Low blur effect and high light extraction efficiency enhancement of organic light emitting displays with novel microstructure attachment," Soc. Inf. Display Tech. Digest 38, 867-870 (2007).
[CrossRef]

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Figures (9)

Fig. 1.
Fig. 1.

The propagation of light rays in (a) the planar and (b) the corrugated substrates. (c) The schematics of the light rays in the waveguide mode extracted from an OLED with a microlens array attachment.

Fig. 2.
Fig. 2.

The fabrication process of microlens arrays.

Fig. 3.
Fig. 3.

The OLEDs attached (a) without, and with (b) a regular and (c) a center-hollowed microlens array.

Fig. 4.
Fig. 4.

The relationships between the relative luminance at normal direction and the pixel size of the OLEDs attached with regular microlens arrays: (a) experimental and (b) simulated results.

Fig. 5.
Fig. 5.

Microphotograph of a duplicated center-hollowed microlens array (tilting angle: 60°).

Fig. 6.
Fig. 6.

The behavior of the relative luminance at normal direction versus the pixel size of the OLEDs attached with the same patterned microlens array.

Fig. 7.
Fig. 7.

The angular-dependent luminance of the OLED attached with a regular microlens array or with a center-hollowed array.

Fig. 8.
Fig. 8.

Photographs of the OLED attached (a) without microlenses and with (b) a center-hollowed or (c) a regular microlens array.

Fig. 9.
Fig. 9.

(a) The spectra and (b) CIE indices of the OLED attached without and with microlens arrays.

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