Naoyuki Ueda

High performance OLED panels for Sony CLIE PDA: development of red emitter and super top emission structure

Sony has commercialized a full-color OLED comprising a new red emissive material, which provides high performance and long operation lifetime. We have carried out systematic research and developed a promising material that has excellent properties for practical applications. This compound shows an absorption peak and a luminescence peak at 483 nm and 644 nm, respectively. The molar absorption coefficient is large (ε = 38,100 M-1cm-1 in 1,4-dioxane) and the fluorescence quantum yield is also very high (QYf =0.82 in 1,4-dioxane). The glass transition temperature is as high as 135 °C. This compound offers thermally stable amorphous state in vacuum coating and is emissive even in single component films. We incorporated the new styryl compound in Sonys proprietary Super Top Emission technology and achieved outstanding brightness and wide color gamut comparable to the NTSC standard. The Super Top Emission consists of a top emitting device structure and color filters, which realize sufficient brightness and pure color at the same time without impairing the wide viewing angles. We obtained suitable device performance for practical use by tuning the layered structures. The emitting color is adjusted by optimizing the doping concentration of the styryl compound in the emitting layer and each thickness of the organic layers. We achieved the chromaticity (0.65, 0.35) in the CIE 1931 standard colorimetric system. The device operation lifetime exceeds 64,000 hours at the initial luminance 500 cd/m2. We would also like to discuss the advantages over the conventional red emissive materials.