Electron injection layers

J. Kido and T. Matsumoto, Bright organic electroluminescent devices having a metal doped electron injection layer, Appl. Phys. Lett., 73 2866-2868 (1998). 

Figure 3.26. Structure of an OLED. S = substrate (glass), ANO = anode (e.g., ITO — indium tin oxide), HIL = hole injection layer (e.g., Cu phthalocyanine), HTL = hole transport layer, EML = emission layer, ETL = electron transport layer, EIL = electron injection layer (e.g., LiF), KAT = cathode (e.g., Ag Mg, Al). The light that is generated by the recombination of holes and electrons is coupled out via the transparent anode.

Thin films containing electron injecting layers of low crystalline oxadiazole derivatives, (V) and (VI), were prepared by Saitoh [4] and used in electroluminescence device. 

The phosphorescent organic light emitting diodes (PHOLEDs) based on Ir(dmp>py)3 complexes were fabricated by the vacuum deposition technique with the following configuration ITO/copper phthalocyanine (CuPc, 10 nm) as hole injection layer/4,4 -bis[(l-naphthyl)(phenyl)-amino]-l,l -biphenyl (NPD, 40 nm) as hole transport layer/CBP Ir(dmppy)3 (8%) (20 nm) as emissive layer/2,9-dimethyl-4,7-diphenyl-l,10-phenanthroline (BCP, 10 nm) as a hole blocking layer/ tris-(8-hydroxyquinoline)aluminum (Alqs, 40 nm) as an electron transport layer/LiF (1 nm) as electron injection layer/ A1 (100... 

The energy level diagrams for various inverted configurations are illustrated in Figure 11.16b. Based on above information, we can treat V2O5 as a hole injection layer with "effective" work function of 5.0eV and CS2CO3 as an electron injection layer with very low work funchon, both of which provide ohmic contacts to the active layer. The polarity of the device is decided by the relative positions of these two interfacial layers and is insensitive to the conduchng electrodes. 

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