In Situ Observation of Degradation by Ligand Substitution in Small-Molecule Phosphorescent Organic Light-Emitting Diodes

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• 作者：Matthew J. Jurow ; Alberto Bossi ; Peter I. Djurovich ; Mark E. Thompson
• 刊名：Chemistry of Materials
• 出版年：2014
• 出版时间：November 25, 2014
• 年：2014
• 卷：26
• 期：22
• 页码：6578-6584
• 全文大小：403K
• ISSN：1520-5002

文摘

Solutions of facial-tris(1-phenylpyrazole)Ir(III) (fac-Ir(ppz)₃), when dissolved in either tert-butyl isocyanide or in solid films of 2-naphthylisocyanide, undergo replacement of a ppz ligand by the isocyanide molecules after irradiation with UV light as demonstrated by liquid chromatograph mass spectrometer analysis. Similarly, solutions of Ir(ppz)₃ and bathophenanthroline (BPhen) in CH₂Cl₂ or acetone-d₆ form a brightly emissive species, [Ir(ppz)₂(Bphen)]⁺ when irradiated with UV light as established by optical, mass, and ¹H nuclear magnetic resonance spectroscopy. Electroluminescent data from blocked organic light-emitting diode (OLED) devices demonstrate that both mer- and fac-(Ir(ppz)₃) dissociate a ligand and coordinate a neighboring BPhen molecule when the device is operated at moderate to high current levels. These experiments offer direct evidence of the dissociation of a metal鈥搇igand bond and subsequent ligand substitution as a degradation pathway in active OLED devices during operation and provide a route to assay in situ the stability of future dopants.