Park Joong-Mok, Gan Zhengqing, Leung Wai Y, Liu Rui, Ye Zhuo, Constant Kristen, Shinar Joseph, Shinar Ruth, Ho Kai-Ming
Ames Laboratory - USDOE, Iowa State University, Ames, Iowa 50011, USA.
Opt Express. 2011 Jul 4;19 Suppl 4:A786-92. doi: 10.1364/OE.19.00A786.
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 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.
非常均匀的2μm间距方形微透镜阵列（μLA），压印在涂有铟锡氧化物（ITO）的1.1mm厚玻璃的空白玻璃面上，用于将有机发光二极管（OLED）的光提取效率提高约100%，显著高于先前报道的提高幅度。阵列设计以及相对于OLED像素尺寸的大小似乎是造成这种提高的原因。这些阵列是通过将聚二甲基硅氧烷（PDMS）模具（其本身由从光刻胶的全息干涉光刻产生的镍母版印章获得）非常经济地软光刻压印在放置在玻璃上的可紫外固化聚氨酯液滴上制成的。然后在ITO上制造绿色和蓝色OLED以完成器件。当μLA约为15×15mm²，即远大于约3×3mm²的OLED像素时，正向电致发光（EL）提高约100%。同样，一个19×25mm²的μLA将从2×2mm²的OLED像素的3×3阵列中提取的EL提高了96%。包括有机层和ITO层中吸收效应的模拟与实验结果一致，并表明0.7mm厚的更薄玻璃将产生约140%的提高。
