New Fluorene Derivatives for Blue Electroluminescent Devices: Influence of Substituents on Thermal Properties, Photoluminescence, and Electroluminescence

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• 作者：Zhaokuai Peng ; Silu Tao ; Xiaohong Zhang ; Jianxin Tang ; Chun Sing Lee ; Shuit-Tong Lee
• 刊名：Journal of Physical Chemistry C
• 出版年：2008
• 出版时间：February 14, 2008
• 年：2008
• 卷：112
• 期：6
• 页码：2165 - 2169
• 全文大小：158K
• 年卷期：v.112,no.6(February 14, 2008)
• ISSN：1932-7455

文摘

A new series of fluorene derivatives with different substituents at the C-2,7- and C-9 positions has beensynthesized and characterized with respect to their luminescence and thermal properties. It was found thatsubstitutions at the C-2,7 positions significantly affected the thermal properties and optical properties, whereassubstitutions at the C-9 position mainly affected the thermal properties of the fluorene derivatives. Organiclight-emitting diodes (OLEDs) with a structure of indium tin oxide (ITO)/copper phthalocyanine (CuPc) (15nm)/4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (NPB) (50 nm)/fluorene derivative (30 nm)/tris(8-quinolinolato)aluminum (Alq₃) (50 nm)/Mg/Ag (200 nm) were fabricated. OLEDs based on the naphthyl-substituted fluorenes gave saturated blue emission centered at 452 nm, while those based on anthryl-substitutedfluorenes showed a blue-green emission with a wider spectrum. OLEDs based on 2,7-dipyrenyl-9'9-dimethylfluorene (DPF) exhibited blue emission with a maximum efficiency of 4.8 cd/A and CIE coordinatesof x = 0.17 and y = 0.24. A similar DPF-based device with an additional hole block layer exhibited betterblue emission with a maximum efficiency of 5.2 cd/A and CIE coordinates of x = 0.15 and y = 0.21, whichare among the best values ever reported for blue OLEDs without a dopant based on fluorescence molecules.The results show that fluorenes with suitable substitutents can act as blue-emitting materials with a highthermal stability and high electroluminescence efficiency.