Enhanced Coupling of Light from Organic Electroluminescent Device Using Diffusive Particle Dispersed High Refractive Index Resin Substrate |
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Authors: | Toshitaka Nakamura Hironaka Fujii Noriyuki Juni Naoto Tsutsumi |
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Institution: | (1) Department of Polymer Science and Engineering, Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto 606-8585, Japan;(2) Core Technology Center, Nitto Denko Corporation, 1-1-2 Shimohozumi, Ibaraki, Osaka 567-8680, Japan |
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Abstract: | To improve light extraction from organic electroluminescent (EL) devices, we introduced a diffusive substrate with 25 μm thickness
consisting of high refractive index resin and scattering particles. It is expected that the diffusive substrate with high
refractive index matrix converts the waveguided emission into external emission from both glass substrate and indium-tin-oxide/organic
layer. We used the ray tracing method to optimize the scattering effect and to verify the coupling out effect of the diffusive
high refractive index substrate. With the use of the ray tracing calculation, an increase in the external emission up to a
factor of 2.7 was expected compared to use of a common glass substrate. Experimentally, the coupling out effect of the diffusive
high refractive index substrate strongly depended on the thickness of electron transporting layer (ETL) due to the well-known
interference effect. The current efficiency increased by a factor of 1.3 for an organic EL device with a 60-nm-thick ETL and
by a factor of 6.8 for one with a 120-nm-thick ETL. |
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Keywords: | organic electroluminescent device high refractive index scattering particle wave-guided light |
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