Organic light-emitting diodes fabricated on recessed anodes for light extraction enhancement

Hsu, Ching-Ming; Wu, Wen-Tuan; Zeng, Yin-Xing; Lin, Bo-Ting; Lin, Wei-Ming

doi:10.1016/j.orgel.2014.12.024

Cited by 10 publications

(1 citation statement)

References 28 publications

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“…The low light extraction efficiency (∼20%) of conventional bottom-emitting OLED caused by the total internal reflection at indium tin oxide (ITO) (n∼2.0)/glass (n∼1.5) and glass/air interfaces is one of the barriers to achieving high efficiency OLED [7]. Extraction of wave guiding modes employing photonic crystals [8][9][10], higher refractive index substrate, corrugated structures [11,12], nano-honeycomb structures on ITO [13], inverted pyramid [14] has been reported and the significant enhancement in light extraction has been achieved [8][9][10][11][13][14][15][16][17].…”

Section: Introductionmentioning

confidence: 99%

Frustrated total internal reflection in organic light-emitting diodes employing sphere cavity embedded in polystyrene

Zhu

2016

J. Opt.

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The light extraction efficiency of top-emitting organic light-emitting diodes (OLEDs) is numerically investigated employing the finite-difference time-domain method. The periodic nanostructures formed by embedding the sphere arrays in polystyrene (PS) are placed on top of OLED to frustrate the total internal reflection at the interface between OLED and free space. These nanostructures serve as an intermediate medium to extract the light out of OLED devices. Efficiently coupling both evanescent waves and propagation waves into spheres and subsequently extracting these light waves out of the sphere is key to achieving high extraction efficiency. By tuning the thickness of PS layer, both of the in-coupling efficiency and out-coupling efficiency are optimized for achieving high light extraction efficiency. Thicker PS layer results in higher in-coupling efficiency in sphere while the thinner PS layer leads to higher out-coupling efficiency. Thus the maximum light extraction is a trade-off between the in-coupling efficiency and out-coupling efficiency. The study shows that light extraction efficiency of 89% can be achieved by embedding 0.90 μm TiO2 sphere in 0.30 μm PS layer with optimized in-coupling efficiency, out-coupling efficiency and cavity effect.

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