Abstract

Very uniform 2 μm-pitch square microlens arrays (μLAs), embossed on the blank glass side of an indium-tin-oxide (ITO)-coated 1.1 mm-thick glass, are used to enhance light extraction from organic light-emitting diodes (OLEDs) by ~100%, significantly higher than enhancements reported previously. The array design and size relative to the OLED pixel size appear to be responsible for this enhancement. The arrays are fabricated by very economical soft lithography imprinting of a polydimethylsiloxane (PDMS) mold (itself obtained from a Ni master stamp that is generated from holographic interference lithography of a photoresist) on a UV-curable polyurethane drop placed on the glass. Green and blue OLEDs are then fabricated on the ITO to complete the device. When the μLA is ~15 × 15 mm2, i.e., much larger than the ~3 × 3 mm2 OLED pixel, the electroluminescence (EL) in the forward direction is enhanced by ~100%. Similarly, a 19 × 25 mm2 μLA enhances the EL extracted from a 3 × 3 array of 2 × 2 mm2 OLED pixels by 96%. Simulations that include the effects of absorption in the organic and ITO layers are in accordance with the experimental results and indicate that a thinner 0.7 mm thick glass would yield a ~140% enhancement.

© 2011 OSA

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  1. 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(13), 1650–1652 (2000).
    [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(5), 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(23), 5777–5782 (2004).
    [CrossRef] [PubMed]
  4. Y. Sun and S. R. Forrest, “Enhanced light out-coupling of organic light-emitting devices using embedded low-index grids,” Nat. Photonics 2(8), 483–487 (2008).
    [CrossRef]
  5. H. J. Peng, Y. L. Ho, C. F. Qiu, M. Wong, and H. S. Kwok, “Coupling efficiency enhancement of organic light emitting devices with refractive microlens array on high index glass substrate,” SID J. 11(4), 158–161 (2004).
    [CrossRef]
  6. 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. Displ. Technol. 1(2), 278–282 (2005).
    [CrossRef]
  7. J. Lim, S. S. Oh, D. Y. Kim, S. H. Cho, I. T. Kim, S. H. Han, H. Takezoe, E. H. Choi, G. S. Cho, Y. H. Seo, S. O. Kang, and B. Park, “Enhanced out-coupling factor of microcavity organic light-emitting devices with irregular microlens array,” Opt. Express 14(14), 6564–6571 (2006).
    [CrossRef] [PubMed]
  8. 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, and T.-C. Wu, “Patterned microlens array for efficiency improvement of small-pixelated organic light-emitting devices,” Opt. Express 16(15), 11044–11051 (2008).
    [CrossRef] [PubMed]
  9. 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]
  10. S.-H. Eom, E. Wrzesniewski, and J. Xue, “Periodic nanostructuring for guided mode extraction in organic light-emitting diodes,” Int. J. Photoenergy 1, 011002 (2011).
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    [CrossRef]
  12. X.-M. Zhao, Y. Xia, and G. M. Whitesides, “Fabrication of three-dimensional micro-structures: microtransfer molding,” Adv. Mater. 8(10), 837–840 (1996).
    [CrossRef]
  13. J.-M. Park, K. S. Nalwa, W. Leung, K. Constant, S. Chaudhary, and K.-M. Ho, “Fabrication of metallic nanowires and nanoribbons using laser interference lithography and shadow lithography,” Nanotechnology 21, 215301 (2010).
    [CrossRef] [PubMed]
  14. Y.-K. Ee, P. Kumnorkaew, R. A. Arif, H. Tong, J. F. Gilchrist, and N. Tansu, “Light extraction efficiency enhancement of InGaN quantum wells light-emitting diodes with polydimethylsiloxane concave microstructures,” Opt. Express 17(16), 13747–13757 (2009).
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    [CrossRef]
  16. B. Choudhury, R. Shinar, and J. Shinar, “Glucose biosensors based on organic light-emitting devices structurally integrated with a luminescent sensing element,” J. Appl. Phys. 96(5), 2949–2954 (2004).
    [CrossRef]
  17. J. Shinar and R. Shinar, “Organic light-emitting devices (OLEDs) and OLED-based chemical and biological sensors: an overview,” J. Phys. D Appl. Phys. 41(13), 133001 (2008).
    [CrossRef]

2011

S.-H. Eom, E. Wrzesniewski, and J. Xue, “Periodic nanostructuring for guided mode extraction in organic light-emitting diodes,” Int. J. Photoenergy 1, 011002 (2011).

2010

J.-M. Park, K. S. Nalwa, W. Leung, K. Constant, S. Chaudhary, and K.-M. Ho, “Fabrication of metallic nanowires and nanoribbons using laser interference lithography and shadow lithography,” Nanotechnology 21, 215301 (2010).
[CrossRef] [PubMed]

2009

2008

J. Shinar and R. Shinar, “Organic light-emitting devices (OLEDs) and OLED-based chemical and biological sensors: an overview,” J. Phys. D Appl. Phys. 41(13), 133001 (2008).
[CrossRef]

Y. Sun and S. R. Forrest, “Enhanced light out-coupling of organic light-emitting devices using embedded low-index grids,” Nat. Photonics 2(8), 483–487 (2008).
[CrossRef]

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, and T.-C. Wu, “Patterned microlens array for efficiency improvement of small-pixelated organic light-emitting devices,” Opt. Express 16(15), 11044–11051 (2008).
[CrossRef] [PubMed]

2007

J.-H. Lee, W. Leung, J. Ahn, T. Lee, I.-S. Park, K. Constant, and K.-M. Ho, “Layer-by-layer photonic crystal fabricated by low-temperature atomic layer deposition,” Appl. Phys. Lett. 90, 151101 (2007).
[CrossRef]

2006

2005

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. Displ. Technol. 1(2), 278–282 (2005).
[CrossRef]

2004

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(23), 5777–5782 (2004).
[CrossRef] [PubMed]

H. J. Peng, Y. L. Ho, C. F. Qiu, M. Wong, and H. S. Kwok, “Coupling efficiency enhancement of organic light emitting devices with refractive microlens array on high index glass substrate,” SID J. 11(4), 158–161 (2004).
[CrossRef]

B. Choudhury, R. Shinar, and J. Shinar, “Glucose biosensors based on organic light-emitting devices structurally integrated with a luminescent sensing element,” J. Appl. Phys. 96(5), 2949–2954 (2004).
[CrossRef]

2002

S. Möller and S. R. Forrest, “Improved light out-coupling in organic light emitting diodes employing ordered microlens arrays,” J. Appl. Phys. 91(5), 3324–3327 (2002).
[CrossRef]

2001

L. Zou, V. Savvate’ev, J. Booher, C. H. Kim, and J. Shinar, “Combinatorial fabrication and studies of intense efficient ultraviolet–violet organic light-emitting device arrays,” Appl. Phys. Lett. 79(14), 2282 (2001).
[CrossRef]

2000

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(13), 1650–1652 (2000).
[CrossRef]

1996

X.-M. Zhao, Y. Xia, and G. M. Whitesides, “Fabrication of three-dimensional micro-structures: microtransfer molding,” Adv. Mater. 8(10), 837–840 (1996).
[CrossRef]

Ahn, J.

J.-H. Lee, W. Leung, J. Ahn, T. Lee, I.-S. Park, K. Constant, and K.-M. Ho, “Layer-by-layer photonic crystal fabricated by low-temperature atomic layer deposition,” Appl. Phys. Lett. 90, 151101 (2007).
[CrossRef]

Arif, R. A.

Booher, J.

L. Zou, V. Savvate’ev, J. Booher, C. H. Kim, and J. Shinar, “Combinatorial fabrication and studies of intense efficient ultraviolet–violet organic light-emitting device arrays,” Appl. Phys. Lett. 79(14), 2282 (2001).
[CrossRef]

Chaudhary, S.

J.-M. Park, K. S. Nalwa, W. Leung, K. Constant, S. Chaudhary, and K.-M. Ho, “Fabrication of metallic nanowires and nanoribbons using laser interference lithography and shadow lithography,” Nanotechnology 21, 215301 (2010).
[CrossRef] [PubMed]

Chen, K.-Y.

Cho, G. S.

Cho, S. H.

Choi, E. H.

Choudhury, B.

B. Choudhury, R. Shinar, and J. Shinar, “Glucose biosensors based on organic light-emitting devices structurally integrated with a luminescent sensing element,” J. Appl. Phys. 96(5), 2949–2954 (2004).
[CrossRef]

Constant, K.

J.-M. Park, K. S. Nalwa, W. Leung, K. Constant, S. Chaudhary, and K.-M. Ho, “Fabrication of metallic nanowires and nanoribbons using laser interference lithography and shadow lithography,” Nanotechnology 21, 215301 (2010).
[CrossRef] [PubMed]

J.-H. Lee, W. Leung, J. Ahn, T. Lee, I.-S. Park, K. Constant, and K.-M. Ho, “Layer-by-layer photonic crystal fabricated by low-temperature atomic layer deposition,” Appl. Phys. Lett. 90, 151101 (2007).
[CrossRef]

Ee, Y.-K.

Eom, S.-H.

S.-H. Eom, E. Wrzesniewski, and J. Xue, “Periodic nanostructuring for guided mode extraction in organic light-emitting diodes,” Int. J. Photoenergy 1, 011002 (2011).

Fang, J.-H.

Forrest, S. R.

Y. Sun and S. R. Forrest, “Enhanced light out-coupling of organic light-emitting devices using embedded low-index grids,” Nat. Photonics 2(8), 483–487 (2008).
[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]

S. Möller and S. R. Forrest, “Improved light out-coupling in organic light emitting diodes employing ordered microlens arrays,” J. Appl. Phys. 91(5), 3324–3327 (2002).
[CrossRef]

Gilchrist, J. F.

Han, S. H.

Ho, K.-M.

J.-M. Park, K. S. Nalwa, W. Leung, K. Constant, S. Chaudhary, and K.-M. Ho, “Fabrication of metallic nanowires and nanoribbons using laser interference lithography and shadow lithography,” Nanotechnology 21, 215301 (2010).
[CrossRef] [PubMed]

J.-H. Lee, W. Leung, J. Ahn, T. Lee, I.-S. Park, K. Constant, and K.-M. Ho, “Layer-by-layer photonic crystal fabricated by low-temperature atomic layer deposition,” Appl. Phys. Lett. 90, 151101 (2007).
[CrossRef]

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. Displ. Technol. 1(2), 278–282 (2005).
[CrossRef]

H. J. Peng, Y. L. Ho, C. F. Qiu, M. Wong, and H. S. Kwok, “Coupling efficiency enhancement of organic light emitting devices with refractive microlens array on high index glass substrate,” SID J. 11(4), 158–161 (2004).
[CrossRef]

Ho, Y.-H.

Hsu, S.-C.

Kang, S. O.

Kim, C. H.

L. Zou, V. Savvate’ev, J. Booher, C. H. Kim, and J. Shinar, “Combinatorial fabrication and studies of intense efficient ultraviolet–violet organic light-emitting device arrays,” Appl. Phys. Lett. 79(14), 2282 (2001).
[CrossRef]

Kim, D. Y.

Kim, I. T.

Kumnorkaew, P.

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. Displ. Technol. 1(2), 278–282 (2005).
[CrossRef]

H. J. Peng, Y. L. Ho, C. F. Qiu, M. Wong, and H. S. Kwok, “Coupling efficiency enhancement of organic light emitting devices with refractive microlens array on high index glass substrate,” SID J. 11(4), 158–161 (2004).
[CrossRef]

Lee, J.-H.

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, and T.-C. Wu, “Patterned microlens array for efficiency improvement of small-pixelated organic light-emitting devices,” Opt. Express 16(15), 11044–11051 (2008).
[CrossRef] [PubMed]

J.-H. Lee, W. Leung, J. Ahn, T. Lee, I.-S. Park, K. Constant, and K.-M. Ho, “Layer-by-layer photonic crystal fabricated by low-temperature atomic layer deposition,” Appl. Phys. Lett. 90, 151101 (2007).
[CrossRef]

Lee, T.

J.-H. Lee, W. Leung, J. Ahn, T. Lee, I.-S. Park, K. Constant, and K.-M. Ho, “Layer-by-layer photonic crystal fabricated by low-temperature atomic layer deposition,” Appl. Phys. Lett. 90, 151101 (2007).
[CrossRef]

Leung, W.

J.-M. Park, K. S. Nalwa, W. Leung, K. Constant, S. Chaudhary, and K.-M. Ho, “Fabrication of metallic nanowires and nanoribbons using laser interference lithography and shadow lithography,” Nanotechnology 21, 215301 (2010).
[CrossRef] [PubMed]

J.-H. Lee, W. Leung, J. Ahn, T. Lee, I.-S. Park, K. Constant, and K.-M. Ho, “Layer-by-layer photonic crystal fabricated by low-temperature atomic layer deposition,” Appl. Phys. Lett. 90, 151101 (2007).
[CrossRef]

Lim, J.

Lin, H.-Y.

Lu, M.-H.

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(13), 1650–1652 (2000).
[CrossRef]

Madigan, C. F.

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(13), 1650–1652 (2000).
[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(5), 3324–3327 (2002).
[CrossRef]

Nalwa, K. S.

J.-M. Park, K. S. Nalwa, W. Leung, K. Constant, S. Chaudhary, and K.-M. Ho, “Fabrication of metallic nanowires and nanoribbons using laser interference lithography and shadow lithography,” Nanotechnology 21, 215301 (2010).
[CrossRef] [PubMed]

Oh, S. S.

Park, B.

Park, I.-S.

J.-H. Lee, W. Leung, J. Ahn, T. Lee, I.-S. Park, K. Constant, and K.-M. Ho, “Layer-by-layer photonic crystal fabricated by low-temperature atomic layer deposition,” Appl. Phys. Lett. 90, 151101 (2007).
[CrossRef]

Park, J.-M.

J.-M. Park, K. S. Nalwa, W. Leung, K. Constant, S. Chaudhary, and K.-M. Ho, “Fabrication of metallic nanowires and nanoribbons using laser interference lithography and shadow lithography,” Nanotechnology 21, 215301 (2010).
[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. Displ. Technol. 1(2), 278–282 (2005).
[CrossRef]

Peng, H. J.

H. J. Peng, Y. L. Ho, C. F. Qiu, M. Wong, and H. S. Kwok, “Coupling efficiency enhancement of organic light emitting devices with refractive microlens array on high index glass substrate,” SID J. 11(4), 158–161 (2004).
[CrossRef]

Qiu, C. F.

H. J. Peng, Y. L. Ho, C. F. Qiu, M. Wong, and H. S. Kwok, “Coupling efficiency enhancement of organic light emitting devices with refractive microlens array on high index glass substrate,” SID J. 11(4), 158–161 (2004).
[CrossRef]

Savvate’ev, V.

L. Zou, V. Savvate’ev, J. Booher, C. H. Kim, and J. Shinar, “Combinatorial fabrication and studies of intense efficient ultraviolet–violet organic light-emitting device arrays,” Appl. Phys. Lett. 79(14), 2282 (2001).
[CrossRef]

Seo, Y. H.

Shinar, J.

J. Shinar and R. Shinar, “Organic light-emitting devices (OLEDs) and OLED-based chemical and biological sensors: an overview,” J. Phys. D Appl. Phys. 41(13), 133001 (2008).
[CrossRef]

B. Choudhury, R. Shinar, and J. Shinar, “Glucose biosensors based on organic light-emitting devices structurally integrated with a luminescent sensing element,” J. Appl. Phys. 96(5), 2949–2954 (2004).
[CrossRef]

L. Zou, V. Savvate’ev, J. Booher, C. H. Kim, and J. Shinar, “Combinatorial fabrication and studies of intense efficient ultraviolet–violet organic light-emitting device arrays,” Appl. Phys. Lett. 79(14), 2282 (2001).
[CrossRef]

Shinar, R.

J. Shinar and R. Shinar, “Organic light-emitting devices (OLEDs) and OLED-based chemical and biological sensors: an overview,” J. Phys. D Appl. Phys. 41(13), 133001 (2008).
[CrossRef]

B. Choudhury, R. Shinar, and J. Shinar, “Glucose biosensors based on organic light-emitting devices structurally integrated with a luminescent sensing element,” J. Appl. Phys. 96(5), 2949–2954 (2004).
[CrossRef]

Sturm, J. C.

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(13), 1650–1652 (2000).
[CrossRef]

Su, I.-L.

Sun, Y.

Y. Sun and S. R. Forrest, “Enhanced light out-coupling of organic light-emitting devices using embedded low-index grids,” Nat. Photonics 2(8), 483–487 (2008).
[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]

Takezoe, H.

Tansu, N.

Tong, H.

Tsai, J.-H.

Wei, M.-K.

Whitesides, G. M.

X.-M. Zhao, Y. Xia, and G. M. Whitesides, “Fabrication of three-dimensional micro-structures: microtransfer molding,” Adv. Mater. 8(10), 837–840 (1996).
[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. Displ. Technol. 1(2), 278–282 (2005).
[CrossRef]

H. J. Peng, Y. L. Ho, C. F. Qiu, M. Wong, and H. S. Kwok, “Coupling efficiency enhancement of organic light emitting devices with refractive microlens array on high index glass substrate,” SID J. 11(4), 158–161 (2004).
[CrossRef]

Wrzesniewski, E.

S.-H. Eom, E. Wrzesniewski, and J. Xue, “Periodic nanostructuring for guided mode extraction in organic light-emitting diodes,” Int. J. Photoenergy 1, 011002 (2011).

Wu, T.-C.

Xia, Y.

X.-M. Zhao, Y. Xia, and G. M. Whitesides, “Fabrication of three-dimensional micro-structures: microtransfer molding,” Adv. Mater. 8(10), 837–840 (1996).
[CrossRef]

Xue, J.

S.-H. Eom, E. Wrzesniewski, and J. Xue, “Periodic nanostructuring for guided mode extraction in organic light-emitting diodes,” Int. J. Photoenergy 1, 011002 (2011).

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. Displ. Technol. 1(2), 278–282 (2005).
[CrossRef]

Zhao, X.-M.

X.-M. Zhao, Y. Xia, and G. M. Whitesides, “Fabrication of three-dimensional micro-structures: microtransfer molding,” Adv. Mater. 8(10), 837–840 (1996).
[CrossRef]

Zou, L.

L. Zou, V. Savvate’ev, J. Booher, C. H. Kim, and J. Shinar, “Combinatorial fabrication and studies of intense efficient ultraviolet–violet organic light-emitting device arrays,” Appl. Phys. Lett. 79(14), 2282 (2001).
[CrossRef]

Adv. Mater.

X.-M. Zhao, Y. Xia, and G. M. Whitesides, “Fabrication of three-dimensional micro-structures: microtransfer molding,” Adv. Mater. 8(10), 837–840 (1996).
[CrossRef]

Appl. Phys. Lett.

L. Zou, V. Savvate’ev, J. Booher, C. H. Kim, and J. Shinar, “Combinatorial fabrication and studies of intense efficient ultraviolet–violet organic light-emitting device arrays,” Appl. Phys. Lett. 79(14), 2282 (2001).
[CrossRef]

J.-H. Lee, W. Leung, J. Ahn, T. Lee, I.-S. Park, K. Constant, and K.-M. Ho, “Layer-by-layer photonic crystal fabricated by low-temperature atomic layer deposition,” Appl. Phys. Lett. 90, 151101 (2007).
[CrossRef]

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(13), 1650–1652 (2000).
[CrossRef]

Int. J. Photoenergy

S.-H. Eom, E. Wrzesniewski, and J. Xue, “Periodic nanostructuring for guided mode extraction in organic light-emitting diodes,” Int. J. Photoenergy 1, 011002 (2011).

J. Appl. Phys.

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(5), 3324–3327 (2002).
[CrossRef]

B. Choudhury, R. Shinar, and J. Shinar, “Glucose biosensors based on organic light-emitting devices structurally integrated with a luminescent sensing element,” J. Appl. Phys. 96(5), 2949–2954 (2004).
[CrossRef]

J. Displ. Technol.

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. Displ. Technol. 1(2), 278–282 (2005).
[CrossRef]

J. Phys. D Appl. Phys.

J. Shinar and R. Shinar, “Organic light-emitting devices (OLEDs) and OLED-based chemical and biological sensors: an overview,” J. Phys. D Appl. Phys. 41(13), 133001 (2008).
[CrossRef]

Nanotechnology

J.-M. Park, K. S. Nalwa, W. Leung, K. Constant, S. Chaudhary, and K.-M. Ho, “Fabrication of metallic nanowires and nanoribbons using laser interference lithography and shadow lithography,” Nanotechnology 21, 215301 (2010).
[CrossRef] [PubMed]

Nat. Photonics

Y. Sun and S. R. Forrest, “Enhanced light out-coupling of organic light-emitting devices using embedded low-index grids,” Nat. Photonics 2(8), 483–487 (2008).
[CrossRef]

Opt. Express

SID J.

H. J. Peng, Y. L. Ho, C. F. Qiu, M. Wong, and H. S. Kwok, “Coupling efficiency enhancement of organic light emitting devices with refractive microlens array on high index glass substrate,” SID J. 11(4), 158–161 (2004).
[CrossRef]

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Figures (4)

Fig. 1
Fig. 1

(a) Schematic of μLA fabrication on glass. A master template is covered with PDMS. The PDMS is removed from the master and then pressed against a PU drop on another glass substrate. The PDMS is lifted off and the PU microlens array remains on the glass substrate. (b) SEM image of the 2D patterns of photoresist and (c) the resulting PU microlens array.

Fig. 2
Fig. 2

Images of two OLED arrays with (a) green emitting Alq3 and (b) blue emitting DPVBi. The left side pixels in each image are under a microlens array and the right ones are reference pixels. The surrounding (rim) lines are the epoxy sealant used for OLED encapsulation. (c) EL spectra of the Alq3-based OLED with a PU microlens array measured with different apertures of an integrating sphere. (d) EL spectra of a DPVBi-based OLED with microlenses measured with a 25 mm diameter integrating sphere aperature. The black lines in (c) and (d) are the reference spectra of nominally identical OLED pixels without the microlenses.

Fig. 3
Fig. 3

Schematic of light extraction model with microlenses: (a) left: extraction enhancement by the microlens array due to incidence angles change that reduces the total internal reflection inside the glass; right: light waveguiding in the glass in the absence of the microlenses. (b,c) Forward EL intensity of an OLED pixel with the microlens array that is the sum of the slightly diffused emission at the pixel area and the extra emission due to the microlens. (d) Forward intensity of an OLED pixel without microlenses.

Fig. 4
Fig. 4

The EL spectra of the 9 pixels without (open circles) and with (solid squares) the 19 × 25 mm2 PU μLA, and the EL spectrum of the 9 pixels with the μLA (open triangles), obtained from an integrating sphere with 25 mm aperture. All devices were driven at 8 V. Each OLED pixel is 2 × 2 mm2, and adjacent pixels are separated by a 2 mm gap.

Tables (1)

Tables Icon

Table 1 (a)–(c) Calculated ηext Enhancements with Various μLA Areas, Glass Thickness, and Integrating Sphere Apertures a

Equations (1)

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η e x t ~ ( 1 cos θ c ) ~ 1 2 n o r g 2 ,

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