OLEDs based on some mixed-ligand terbium carboxylates and zinc complexes with tetradentate Schiff bases: Mechanisms of electroluminescence degradation

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• 作者：Leonid Lepnev ; Andrei Vaschenko ; Alexei Vitukhnovsky ; Svetlana Eliseeva ; Oxana Kotova ; Natalia Kuzmina
• 关键词：Organic light emitting diodes ; Degradation
• 刊名：Synthetic Metals
• 出版年：2009
• 出版时间：April 2009
• 年：2009
• 卷：159
• 期：7-8
• 页码：625-631
• 全文大小：719 K

文摘

Mixed-ligand terbium carboxylates—Tb(Carb)₃(TPPO)₂ (HCarb = HSal (salicylic acid), Hpobz (2-phenoxybenzoic acid); TPPO = triphenylphosphine oxide) and zinc complexes with tetradentate Schiff bases—ZnSB (H₂SB = H₂SAL1, H₂SAL2 (derivatives of salicylic aldehyde); H₂MO1, H₂MO2 (derivatives of o-vanillin)) were used as electroluminescent (EL) layers in organic light emitting diodes (OLEDs). These devices have undergone reversible and irreversible mechanisms of EL degradation. The reversible one is mainly associated with charge carrier trap filling. At the same time several mechanisms of irreversible degradation were observed under UV light irradiation, heating and ageing in ambient conditions. The degradation mechanisms of OLEDs under heating from 293 K to 320 K were related to the changes in the interface regions. The initial degradation was eliminated by (1) an application of alternating bias voltage; (2) a decrease of the substrate temperature and the velocity of the thermal evaporation of materials. The degradation of OLEDs was not observed under low UV irradiation that is promising for OLEDs operation under day light.