5 December 2006 Blue emitting OLED with star-shaped multifunctional oligomer
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A fluorescent star-shaped oligomer with a nitrogen atom as a core and both a hole transporting arylamine and an electron transporting 1,3,4-oxadiazole moiety, tri(4-(5-phenyl-1, 3, 4-oxadiazol-2-yl)phenyl)amine (TPOPA), has been designed and synthesized using a 5-step reaction procedure. The synthesized compound was characterized by elemental analysis, 1H-NMR and mass spectroscopy. Thermogravimetric (TG) and differential scanning calorimetry (DSC) analysis show that TPOPA exhibits high thermal stability (Td, 373°C) and high glass-transition temperature (Tg, 116 °C). Photoluminescence measurements indicate that the star-shaped oligomer shows intense blue emission peaked at 445 nm with a high quantum yield of 0.68 under near UV light excitation. The HOMO value of TPOPA is -5.64 eV and the LUMO is -2.58 eV based on the electro-chemical determinations. Reversible anodic oxidation results suggest that the hole-transporting is predominant for TPOPA. Two single layered devices were fabricated by vacuum evaporation with configurations of ITO / CuPC (15 nm) / TPOPA (95 nm) / Ca(30 nm) / Al(100 nm) (device 1) and ITO / CuPC(15 nm) / TPOPA (175 nm) / Ca(30 nm) / Al(100 nm) (device 2), where TPOPA was used both as emitter and carrier - transporting material, CuPC as a hole-injection and electron block material. The devices show blue wide-band emission peaked at 438 nm with a maximum luminance of 650 cd/m2 and 512 cd/m2 under an operating voltage of 12 V, respectively.
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Meng Lian Gong, Meng Lian Gong, Neng Jun Xiang, Neng Jun Xiang, K. L. Tong, K. L. Tong, Tik Ho Lee, Tik Ho Lee, Shu Kong So, Shu Kong So, Louis M. Leung, Louis M. Leung, } "Blue emitting OLED with star-shaped multifunctional oligomer", Proc. SPIE 6333, Organic Light Emitting Materials and Devices X, 63331H (5 December 2006); doi: 10.1117/12.679990; https://doi.org/10.1117/12.679990

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