Improvement in Luminance Efficiency by Insertion of Buffer Layers in Flexible Organic Light-Emitting Diodes

概要

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This study employed poly(3,4-ethylenedioxy-thiophene):poly(styrenesulfonate) (PEDOT:PSS), 4,4$'$-bis[N-(1-naphthyl)-N-phenylamino]-biphenyl ($\alpha$-NPD) and $\alpha$-NPD/Teflon as buffer layers between the organic layer and indium tin oxide (ITO) of a flexible organic light-emitting diode (FOLED) to enhance the luminance efficiency of the device. PEDOT:PSS and $\alpha$-NPD were spin-coated onto the ITO substrate, but $\alpha$-NPD was first dissolved in chloroform. With the deposition of PEDOT:PSS of 40 nm thickness, the surface roughness of ITO decreased from 2.768 to 1.415 nm, whereas the luminance yield increased from 2.0 to 4.0 cd/A; the maximum luminance was 1500 cd/m2 at 44 mA/cm2. With the deposition of $\alpha$-NPD of optimum thickness as buffer layer, the device had a luminance yield of 5.2 cd/A and a maximum luminance of 1220 cd/m2 at 25 mA/cm2. When the $\alpha$-NPD buffer layer was further coated with a thin layer of Teflon by evaporation, i.e., $\alpha$-NPD/Teflon (55/1 nm), the luminance yield of the device increased to 6.5 cd/A.
Published by the Japan Society of Applied Physics through the Institute of Pure and Applied Physicsの論文
2006-04-30