Electron transport layer, ETL

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... 

A higher efficiency, yet simpler structure PPLED device fabricated with the same dopant and host materials was almost simultaneously reported by Yang and Tsutsui [35]. The highest EQE of their device ITO/PVK 5%Ir(ppy)3 /OXD-7/Mg Ag (where ITO is indium tin oxide) (using OXD-7 (7) as an electron-transporting layer (ETL), Chart 4.3) reached the value of 7.5%, which was the first reported PLED with external efficiency above 5%, an upper limit of the fluorescent PLEDs. The power efficiency was 5.8 lm/W at the luminance of 106 cd/m2. 

Electron-transfer sensitization, 19 109 Electron transport, between photosystem inhibitors, 13 288 Electron-transport layer (ETL)... 

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 112 Molecular structures (a) of the materials used to manufacture DL LEDs (b) with a molecularly doped hole-transporting-layer (HTL) which serves as an emitter (EML) along with the emitting electron-transporting-layer (ETL).

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.

There are several possibilities for constructing bilayer OLEDs with a more balanced charge injection. These include an electron-transport layer (ETL) and a combined hole-transport (HTL) and emission layer. Conversely a hole-transport layer and a combined electron-transport and emission layer is also effective. 

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 first two-layer device based on a conjugated polymer was demonstrated by Brown et al.39 They introduced an electron-transporting layer (ETL) between PPV and the negative electrode, as shown in Fig. 5.14. The electron-transporting layer used was the molecule 2-(4-biphenylyl)-5-(4-terf-butylphenyl)-l,3,4-oxadiazole, dispersed in a matrix of polymethylmethacrylate. Quantum efficiencies were typically increased by a factor of 10 compared to devices without the electron-transport... 

In the OLEDs there is a high possibility that exciplex formation occurs at the ETL/EML or HTL/EML interfaces because HTL and electron transport layer (ETL) usually have an electron-donating and an electron-accepting nature, respectively. There have been some researches on the application of exciplexes for the tuning of emission colors (Li et al 2006, Liang and Choy 2006) and white emitting OLEDs (Tong et al 2007). Extensive studies on exited bi-molecular complexes and their application in electrophosphorescent devices have been done by Kalinowski et al (2007) and Cocchi et al (2006). 

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