Light extraction efficiency enhancement of InGaN quantum wells light-emitting diodes with polydimethylsiloxane concave microstructures

Ee, Yik-Khoon; Kumnorkaew, Pisist; Arif, Ronald A.; Tong, Hua; Gilchrist, James F.; Tansu, Nelson

doi:10.1364/oe.17.013747

Cited by 129 publications

(77 citation statements)

References 26 publications

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“…1(b), the top of the structure is not quite as spherical as that for an optimal microlens, but this is remedied by heating the sample on a hot plate to 140°C for 60 seconds. Note that such an inverse pattern was reported as a light extraction layer for an InGaN LED [14]. Figure 1(c) is an SEM image of the μLA having spherical shapes.…”

Section: Resultsmentioning

confidence: 64%

Soft holographic interference lithography microlens for enhanced organic light emitting diode light extraction

Park¹,

Gan²,

Leung³

et al. 2011

Opt. Express

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Very uniform 2 μm-pitch square microlens arrays (μLAs), embossed on the blank glass side of an indium-tinoxide (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 mm 2 , i.e., much larger than the ~3 × 3 mm 2 OLED pixel, the electroluminescence (EL) in the forward direction is enhanced by ~100%. Similarly, a 19 × 25 mm 2 μLA enhances the EL extracted from a 3 × 3 array of 2 × 2 mm 2 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. 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 lightemitting 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 mm 2 , i.e., much larger than the ~3 × 3 mm 2 OLED pixel, the electroluminescence (EL) in the forward direction is enhanced by ~100%. Similarly, a 19 × 25 mm 2 μLA enhances the EL extracted from a 3 × 3 array of 2 × 2 mm 2 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. Keywords

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Section: Resultsmentioning

confidence: 64%

Soft holographic interference lithography microlens for enhanced organic light emitting diode light extraction

Park¹,

Gan²,

Leung³

et al. 2011

Opt. Express

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show abstract

“…Various approaches have been adopted to extract the trapped light in the LED, and great efforts have been made in incorporating photonic crystal (PhC) into GaN-based LED to improve the light extraction [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. Shallow etched PhC gratings are employed on the surface of different materials, such as GaN [1, 2,4], indium tin oxide (ITO) [9,10], or thin polymer layer [11,12]. In most publications, the strategy of using a PhC grating mainly relies on Bragg diffraction of the trapped guided modes from the LEDs.…”

Section: Introductionmentioning

confidence: 99%

Lattice constant effects of photonic crystals on the extraction of guided mode of GaN based light emitting diodes

Bei

Kang

et al. 2010

Sci. China Technol. Sci.

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We have fabricated a series of square-lattice hole photonic crystal (2PhC) arrays simultaneously at the un-current injection region on a special sample of GaN based light emitting diode (LED) by using focus ion beam milling (FIBM). The lattice constants of the 2PhC arrays vary from 230 to 1500 nm, while the 2PhC arrays have a constant area of about 9 μm ×18 μm and a fixed depth of 150±10 nm which approaches but does not penetrate the active layer. Microscopic electroluminescence images and spectral measurements consistently confirm that the top emitting intensities from different 2PhCs are all enhanced compared with the unpatterned region. It is demonstrated that the output coupling of propagating guided modes is realized by the diffracted transmission of the 2PhCs. The enhancement factors of the guided modes compared with the unpatterned region are plotted as function of the lattice constant. It is found that the highest enhancements for the extraction of guided modes were obtained for the lattice constant of 230 and 460 nm of 2PhCs. The results are discussed by the two-dimensional rigorous coupled wave analysis (RCWA). photonic crystal, guided modes, lattice pitches, GaN-based light emitting diodes Citation: Fu X X, Zhang B, Kang X N, et al. Lattice constant effects of photonic crystals on the extraction of guided mode of GaN based light emitting diodes.

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“…Antireflective subwavelength structures (ARS) have been proved as an ideal approach to enhance the light transmittance over a broad spectral bandwidth [14][15][16][17][18][19]. In addition, several recent works to increase the light extraction efficiency in GaN-based LEDs had been demonstrated by using photonic crystals with large index contrast [20], and self-assembled colloidal microlens arrays [3,21,22]. In the present work, applying pseudoperiodic ARS on the fluorescent SiC to enhance the light extraction efficiency over the entire visible spectral range has been studied.…”

mentioning

confidence: 99%

Omnidirectional luminescence enhancement of fluorescent SiC via pseudoperiodic antireflective subwavelength structures

Jokubavičius

Yakimova

et al. 2012

Opt. Lett.

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Light extraction efficiency enhancement of InGaN quantum wells light-emitting diodes with polydimethylsiloxane concave microstructures

Cited by 129 publications

References 26 publications

Soft holographic interference lithography microlens for enhanced organic light emitting diode light extraction

Soft holographic interference lithography microlens for enhanced organic light emitting diode light extraction

Lattice constant effects of photonic crystals on the extraction of guided mode of GaN based light emitting diodes

Omnidirectional luminescence enhancement of fluorescent SiC via pseudoperiodic antireflective subwavelength structures

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