Contact formation of LiF/Al cathodes in Alq-based organic light-emitting diodes
Contact formation of LiF/Al cathodes in Alq-based organic light-emitting diodes
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DOI：
10.1088/0022-3727/35/2/302
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发表时间：
2002-01
期刊：
影响因子：
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通讯作者：
L. Hung;Ruiqin Q. Zhang;P. He;G. Mason
中科院分区：
文献类型：
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作者：
L. Hung;Ruiqin Q. Zhang;P. He;G. Mason
本文系统地研究了在三（8-羟基喹啉）铝（Alq）上沉积LiF/Al双层膜形成有机电致发光器件中有效的电子注入接触。在LiF/Al双层阴极和LiF掺杂的Al复合阴极中都观察到了高效的电子注入。紫外光电子能谱分析表明LiF/Al和LiF掺杂Al/Alq的界面化学性质具有很强的相似性。高分辨率电子能量损失谱的测量显示有限的界面反应的LiF上的Al和Alq，而一个强烈的衰减的损失峰相关的Li-F的拉伸模式后，观察到沉积的Alq/LiF上的Al-Al膜。结果表明，这种接触是由于化学反应而形成的，反应层的厚度小于1 nm，分子轨道计算表明，Li的释放以及随后与Alq的反应在热力学上是允许的。浅接触的性质允许在阴极结构的设计和各种器件配置的潜在应用中具有更大的灵活性。
A systematic study has been carried out on the formation of an effective electron-injecting contact by depositing an LiF/Al bilayer on tris-(8-hydroxyquinoline) aluminium (Alq) in organic light-emitting diodes. Efficient electron injection is observed in both a LiF/Al bilayer cathode and an LiF-doped Al composite cathode. An analysis with ultraviolet photoelectron spectroscopy reveals a strong similarity in interface chemistry between LiF/Al and LiF-doped Al on Alq. Measurements with high-resolution electron energy loss spectroscopy show limited interfacial reaction of LiF on both Al and Alq, whereas a strong attenuation of the loss peak related to the Li-F stretch mode is observed after depositing an ultrathin Al film on Alq/LiF. The results indicate that the contact is formed as a consequence of chemical reaction with a reacted layer of 1 nm or less. Molecular orbital calculation suggests that the release of Li and subsequent reaction with Alq is thermodynamically allowed. The shallow-contact nature allows for much greater flexibility in the design of cathode structures and potential applications to various device configurations.