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Optics Express

Optics Express

  • Editor: C. Martijn de Sterke
  • Vol. 16, Iss. 15 — Jul. 21, 2008
  • pp: 11044–11051

Optics InfoBase > Optics Express > Volume 16 > Issue 15 > Page 11044

Patterned microlens array for efficiency improvement of small-pixelated organic light-emitting devices

Hoang-Yan Lin, Yu-Hsuan Ho, Juin-Haw Lee, Kuan-Yu Chen, Jheng-Hao Fang, Sheng-Chih Hsu, Mao-Kuo Wei, Hung-Yi Lin, Jen-Hui Tsai, and Tung-Chuan Wu  »View Author Affiliations


Optics Express, Vol. 16, Issue 15, pp. 11044-11051 (2008)
http://dx.doi.org/10.1364/OE.16.011044


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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

OCIS Codes
(080.3630) Geometric optics : Lenses
(230.3990) Optical devices : Micro-optical devices

ToC Category:
Geometric optics

History
Original Manuscript: April 24, 2008
Revised Manuscript: June 25, 2008
Manuscript Accepted: July 6, 2008
Published: July 9, 2008

Citation
Hoang-Yan Lin, Yu-Hsuan Ho, Juin-Haw Lee, Kuan-Yu Chen, Jheng-Hao Fang, Sheng-Chih Hsu, Mao-Kuo Wei, Hung-Yi Lin, Jen-Hui Tsai, and Tung-Chuan Wu, "Patterned microlens array for efficiency improvement of small-pixelated organic light-emitting devices," Opt. Express 16, 11044-11051 (2008)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-16-15-11044


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References

  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]

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