Light electron-transporting layer

The simplest manifestation of an OLED is a sandwich structure consisting of an emission layer (EML) between an anode and a cathode. More typical is an increased complexity OLED structure consisting of an anode, an anode buffer or hole injection layer (HIL), a hole transport layer (HTL), a light-emitting layer, an electron transport layer (ETL), a cathode... 

N. Donze, P. Pechy, M. Gratzel, M. Schaer, and L. Zuppiroli, Quinolinate zinccomplexes as electron transporting layers in organic light-emitting diodes, Chem. Phys. Lett., 315 405-410 (1999). 

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.

Fournet P, Coleman JN, Lahr B, Drury A, Blau WJ, O Brien DF, Horhold HH (2001). Enhanced brightness in organic light-emitting diodes using a carbon nanotube composite as an electron-transport layer. J. Appl. Phys. 90 969-975. 

A typical vaponr deposited EL device consists of a glass snbstrate coated with a conducting transparent indinm tin oxide electrode, on top of which is a 100-500 A hole transport layer (HTL), followed by a thin (= 100 A) light emitting layer (EML), then a 100-500 A electron transport layer (ETL) and finally a cathode of an alloy such as Mg Ag. This is illustrated in Fignre 3.32. 

Figure 4.8 Schematic representation some of the elements of a generalised multilayer organic light-emitting diode (OLED) with direct addressing. The thin metallic cathode segments are connected directly to the electron-transport layer (ETL). The impermeable encapsulation is not shown.

A thin film ( 100 nm) of a polymer hole-transport layer (HTL) supports a second thin film of a polymer electron-transport layer (ETL) sandwiched between two electrodes supported on a substrate, see Figures 6.2 and 6.3. The anode is transparent in order to allow the passage of the light generated. A potential can be applied between the electrodes. The metal cathode has a low... 

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... 

Fig. 5.2 Device configuration and working principle of OLEDs. (a) a triple-layer device showing a hole-transporting layer (HTL), emissive layer (EML) and electron-transporting layer (ETL) sandwiched between two electrodes (b) a double-layer device. An energy diagram showing hopping transport of holes and electrons in (c) a triple-layer device and (d) a double-layer device. Light comes out upon radiative decay of excitons.

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