Abstract

We demonstrated a new approach to fabricate microlens arrays attached to an organic light-emitting diode (OLED) to improve the outcoupling efficiency. Polydimethylsiloxane (PDMS) microlens arrays were fabricated by imprint lithography. Two kinds of photoresists were used to make a mold to imprint the microlens array. Using this simple and low-cost fabrication process, a maximum of 43% luminance enhancement was acquired with the green OLED. When attaching the microlens array to a green OLED, the efficacy and power efficiency were increased by 42% and 69% at 900 cd/m<sup>2</sup>, respectively. The external quantum efficiency of the OLED with the microlens array was increased by 59% at 7.5 mA/cm<sup>2</sup> due to luminance enhancement at a large viewing angle without spectral change. Additionally, the image blur problem is quantitatively analyzed by defining “blur width.” The image blur problem induced by the microlens array is reduced by adopting the microlens array with lower height while the luminance enhancement by the microlens array remained.

© 2011 IEEE

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  1. Y. Sun, S. R. Forrest, "Enhanced light out-coupling of organic light-emitting devices using embedded low-index grids," Nature Photonics 2, 483-487 (2008).
  2. Y. Sun, S. R. Forrest, "Organic light emitting devices with enhanced outcoupling via microlenses fabricated by imprint lithography," J. Appl. Phys. 100, 073106 (2006).
  3. H. Peng, Y. L. Ho, X.-J. Yu, M. Wong, "Coupling efficiency enhancement in organic light-emitting devices using microlens array—Theory and experiment," J. Display Technol. 1, 278-282 (2005).
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  5. K. Ishihara, M. Fujita, I. Matsubara, T. Asano, S. Noda, "Organic light-emitting diodes with photonic crystals on glass substrate fabricated by nanoimprint lithography," Appl. Phys. Lett. 90, 113105 (2007).
  6. S. Möller, S. R. Forrest, "Improved light out-coupling in organic light emitting diodes employing ordered microlens arrays," J. Appl. Phys. 91, 3324-3327 (2002).
  7. S.-K. Lee, "A simple method for microlens fabrication by the modified LIGA process," J. Micromech. Microeng. 12, 334-340 (2002).
  8. T.-W. Lin, C.-F. Chen, J.-J. Yang, Y.-S. Liao, "A dual-directional light-control film with a high-sag and high-asymmetrical-shape microlens array fabricated by a UV imprinting process," J. Micromech. Microeng. 18, 095029 (2008).
  9. E. Roy, B. Voisin, J.-F. Gravel, R. Peytavi, D. Boudreau, T. Veres, "Microlens array fabrication by enhanced thermal reflow process—Towards efficient collection of fluorescence light from microarrays," Microelectron. Eng. 86, 2255-2261 (2009).
  10. H.-Y. Lin, Y.-H. Ho, J.-H. Lee, K.-Y. Chen, J.-H. Fang, S.-C. Hsu, M.-K. Wei, H.-Y. Lin, J.-H. Tsai, T.-C. Wu, "Patterned microlens array for efficiency improvement of small-pixelated organic light-emitting devices," Opt. Express 16, 11044-11051 (2008).
  11. P. Ruffieux, T. Scharf, I. Philipoussis, H. P. Hwezig, R. Voelkel, K. J. Weible, "Two step process for the fabrication of diffraction limited concave microlens arrays," Opt. Express 16, 19451-19549 (2008).
  12. T. Tsutsui, K. Yamamato, "Evaluation of true power luminous efficiency from experimental luminance values," Jpn. J. Appl. Phys. 38, 2799-2803 (1999).
  13. H.-Y. Lin, J.-H. Lee, M.-K. Wei, K.-Y. Chen, S.-C. Hsu, Y.-H. Ho, C.-Y. Lin, "Optical characteristics of the OLED with microlens array film attachment," Proc. of SPIE (2007) pp. 66551H.
  14. S. R. Forrest, D. D. C. Bradley, M. E. Thompson, "Measuring the efficiency of organic light-emitting devices," Adv. Mater. 15, 1043-1048 (2003).
  15. H. Y. Lin, K.-Y. Chen, Y.-H. Ho, J.-H. Fang, S.-C. Hsu, J.-R. Lin, J.-H. Lee, M.-K. Wei, "Luminance and image quality analysis of an organic electroluminescent panel with a patterned microlens array attachment," J. Opt. 12, 085502 (2010).
  16. Y.-H. Ho, K.-Y. Chen, J.-H. Lee, H.-Y. Lin, C.-C. Lin, M.-K. Wei, "Luminance enhancement and blur effect of microlens array film attachment on organic light-emitting device," Conf. Proc.—Lasers and Electro-Optics Society (LEOS) Annu. Meeting (2007) pp. 713-714.

2010 (1)

H. Y. Lin, K.-Y. Chen, Y.-H. Ho, J.-H. Fang, S.-C. Hsu, J.-R. Lin, J.-H. Lee, M.-K. Wei, "Luminance and image quality analysis of an organic electroluminescent panel with a patterned microlens array attachment," J. Opt. 12, 085502 (2010).

2009 (2)

C. S. Kim, M. Kim, D. C. Larrabee, I. Vurgaftman, J. R. Meyer, "Enhanced performance of organic light-emitting diodes using two-dimensional zinc sulfide photonic crystals," J. Appl. Phys. 106, 113105 (2009).

E. Roy, B. Voisin, J.-F. Gravel, R. Peytavi, D. Boudreau, T. Veres, "Microlens array fabrication by enhanced thermal reflow process—Towards efficient collection of fluorescence light from microarrays," Microelectron. Eng. 86, 2255-2261 (2009).

2008 (4)

H.-Y. Lin, Y.-H. Ho, J.-H. Lee, K.-Y. Chen, J.-H. Fang, S.-C. Hsu, M.-K. Wei, H.-Y. Lin, J.-H. Tsai, T.-C. Wu, "Patterned microlens array for efficiency improvement of small-pixelated organic light-emitting devices," Opt. Express 16, 11044-11051 (2008).

P. Ruffieux, T. Scharf, I. Philipoussis, H. P. Hwezig, R. Voelkel, K. J. Weible, "Two step process for the fabrication of diffraction limited concave microlens arrays," Opt. Express 16, 19451-19549 (2008).

Y. Sun, S. R. Forrest, "Enhanced light out-coupling of organic light-emitting devices using embedded low-index grids," Nature Photonics 2, 483-487 (2008).

T.-W. Lin, C.-F. Chen, J.-J. Yang, Y.-S. Liao, "A dual-directional light-control film with a high-sag and high-asymmetrical-shape microlens array fabricated by a UV imprinting process," J. Micromech. Microeng. 18, 095029 (2008).

2007 (1)

K. Ishihara, M. Fujita, I. Matsubara, T. Asano, S. Noda, "Organic light-emitting diodes with photonic crystals on glass substrate fabricated by nanoimprint lithography," Appl. Phys. Lett. 90, 113105 (2007).

2006 (1)

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

2005 (1)

2003 (1)

S. R. Forrest, D. D. C. Bradley, M. E. Thompson, "Measuring the efficiency of organic light-emitting devices," Adv. Mater. 15, 1043-1048 (2003).

2002 (2)

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

S.-K. Lee, "A simple method for microlens fabrication by the modified LIGA process," J. Micromech. Microeng. 12, 334-340 (2002).

1999 (1)

T. Tsutsui, K. Yamamato, "Evaluation of true power luminous efficiency from experimental luminance values," Jpn. J. Appl. Phys. 38, 2799-2803 (1999).

Adv. Mater. (1)

S. R. Forrest, D. D. C. Bradley, M. E. Thompson, "Measuring the efficiency of organic light-emitting devices," Adv. Mater. 15, 1043-1048 (2003).

Appl. Phys. Lett. (1)

K. Ishihara, M. Fujita, I. Matsubara, T. Asano, S. Noda, "Organic light-emitting diodes with photonic crystals on glass substrate fabricated by nanoimprint lithography," Appl. Phys. Lett. 90, 113105 (2007).

J. Appl. Phys. (3)

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

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

C. S. Kim, M. Kim, D. C. Larrabee, I. Vurgaftman, J. R. Meyer, "Enhanced performance of organic light-emitting diodes using two-dimensional zinc sulfide photonic crystals," J. Appl. Phys. 106, 113105 (2009).

J. Display Technol. (1)

J. Micromech. Microeng. (2)

S.-K. Lee, "A simple method for microlens fabrication by the modified LIGA process," J. Micromech. Microeng. 12, 334-340 (2002).

T.-W. Lin, C.-F. Chen, J.-J. Yang, Y.-S. Liao, "A dual-directional light-control film with a high-sag and high-asymmetrical-shape microlens array fabricated by a UV imprinting process," J. Micromech. Microeng. 18, 095029 (2008).

J. Opt. (1)

H. Y. Lin, K.-Y. Chen, Y.-H. Ho, J.-H. Fang, S.-C. Hsu, J.-R. Lin, J.-H. Lee, M.-K. Wei, "Luminance and image quality analysis of an organic electroluminescent panel with a patterned microlens array attachment," J. Opt. 12, 085502 (2010).

Jpn. J. Appl. Phys. (1)

T. Tsutsui, K. Yamamato, "Evaluation of true power luminous efficiency from experimental luminance values," Jpn. J. Appl. Phys. 38, 2799-2803 (1999).

Microelectron. Eng. (1)

E. Roy, B. Voisin, J.-F. Gravel, R. Peytavi, D. Boudreau, T. Veres, "Microlens array fabrication by enhanced thermal reflow process—Towards efficient collection of fluorescence light from microarrays," Microelectron. Eng. 86, 2255-2261 (2009).

Nature Photonics (1)

Y. Sun, S. R. Forrest, "Enhanced light out-coupling of organic light-emitting devices using embedded low-index grids," Nature Photonics 2, 483-487 (2008).

Opt. Express (2)

H.-Y. Lin, Y.-H. Ho, J.-H. Lee, K.-Y. Chen, J.-H. Fang, S.-C. Hsu, M.-K. Wei, H.-Y. Lin, J.-H. Tsai, T.-C. Wu, "Patterned microlens array for efficiency improvement of small-pixelated organic light-emitting devices," Opt. Express 16, 11044-11051 (2008).

P. Ruffieux, T. Scharf, I. Philipoussis, H. P. Hwezig, R. Voelkel, K. J. Weible, "Two step process for the fabrication of diffraction limited concave microlens arrays," Opt. Express 16, 19451-19549 (2008).

Other (2)

H.-Y. Lin, J.-H. Lee, M.-K. Wei, K.-Y. Chen, S.-C. Hsu, Y.-H. Ho, C.-Y. Lin, "Optical characteristics of the OLED with microlens array film attachment," Proc. of SPIE (2007) pp. 66551H.

Y.-H. Ho, K.-Y. Chen, J.-H. Lee, H.-Y. Lin, C.-C. Lin, M.-K. Wei, "Luminance enhancement and blur effect of microlens array film attachment on organic light-emitting device," Conf. Proc.—Lasers and Electro-Optics Society (LEOS) Annu. Meeting (2007) pp. 713-714.

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