Hole injection materials

Hole Injection Materials and Cathode Interfacial Materials. 303... 

HOLE INJECTION MATERIALS AND CATHODE INTERFACIAL MATERIALS 3.3.1 Hole Injection Materials... 

The HIL acts as an interface connection layer between the anode and the HTL so as to improve the film forming property of the subsequent organic layer and to facilitate efficient hole injection. Hole injection materials (HIMs) should have good adhesion to the anode and should serve to smooth the anode surface. The most common HIMs are... 

In electrochemical light-emitting cells, the semiconductive polymer can be surrounded asymmetrically with a hole-injecting material on one side and a low work function electron injecting metal (such as magnesium, calcium, or aluminum) on the other side. The emission of light may occur when a charge carrier recombines in the polymer as electrons from one side and holes from the other meet. 

Using a hole blocking layer, holes can be confined in hole transporting or in hole injecting materials and they can be used as emitters. It minimizes the possibility of... 

TAZ) shown in Figure 11.5, is often added between the layer of luminescent material and the electron-transport layer or the metallic electrode, to balance the charge injection and transport rates. Then the recombination of electrons and holes is confined to the emitting layer and consequently a high electroluminescent efficiency can be obtained. Some hole-injection materials are shown in Figure 11.6. 

Figure 11.6 Structures of some hole-injection materials.

To evaluate hole-transporting ability of newly synthesized phenylnaphthyldiamine derivative HIM 2, we fabricated the hole-dominant device using HTM 2 as a hole-transporting material with structures as follows 1TO/2-TNATA/HTM 2/EML/Al (device 11). On TTO substrate, 4, 4"-tris(N-(naphth-2-yl)-N-phenyl-amino)tri- phenylamine (2-TNATA) was previously deposited as a hole-injecting material. IDE 215 doped with 3 % of IDE 118 (host and dopant materials by Idemitsu Co., LTD) was used as blue emitting layer. 

We performed studies of the deposition of gold, which is widely used as a hole injection material, onto well-defined DIP thin film surfaces to study the interdiffusion using X-ray reflectivity and transmission electron microscopy (Figure 9.9). The study followed the classical approach without specific precaution against interdiffusion except for variation of the temperature and the rate [68, 71, 86-88]. The important result was that under rather typical deposition conditions near room temperature the metal interdiffusion was already significant, and the layers would exhibit electrical shorts, see Figure 9.9b. Only if the... 

The hole injection properties of PA-based compounds were investigated and cross-compared by V, DISCLC, and AS measurements. We demonstrate that PEDOTPSS can act as an excellent hole injection material for PA compounds... 

The surface of ITO can also be modified by deposition of a thin layer of various hole-injection materials (HIM), such as copper phthalocya-nine (CuPc), poly(3,4-ethylene dioxythiophene) (PEDOT), organosilane (CH30)3-Si-C3H7NH2, and many others. Use of an HIM between ITO and the HTL allows for achieving significant improvements in device stability and efficiency. 

Polyaniline was used as hole injection material for polymer hght-emitting devices (PLED) spin-coated from a water-based polyaniline/poly-styrenesulfonate (PAni/PSS) dispersion. Data presented here were based on red, yellow, green, and blue LEPs. Depending on the applied bias voltages, the devices were studied by electrical impedance spectroscopy (EIS) in a wide frequency range. Experimental data could... 

Irvin, G. C. Jagannathan, R. Mehta, R. V Sprout, R. A. Vo, T. T Jagannathan, S. Sadasivan, S. A compressed fluid formulation containing electron transporting, hole injecting material, hole transporting material, and electroluminescent material. Eur. Pat. Appl. EP 1427033, 2004 Chem. Abstr. 2004, 141, 30850. 

Polyaniline Blends. Polyaniline doped with camphor sulfonic acid, PANI-CSA, in the form of a blend with poly(methyl methacrylate), PMMA, is also used as hole injection material in PPV-based LEDs owing to the low barrier for hole injection [209,210] and the match of the PPV electroluminescent emission with the transmittance window of the PANI-CSA/PMMA blend (Fig. 10). Blends of polyester resin (PES) with PANI-CSA were also used for this purpose [209]. The barrier height for hole injection at the PANI-CSA-PES/MEH-PPV blend was found to be dependent on the PANI-CSA concentration, ranging from about 0.02 eV at a concentration of 5% w/w to about 0.1 eV for pure PANI [209]. In the case of PANI-CSA-PMMA/PPV interfaces, the barrier height for hole... 

Another interesting application is to use phthalocyanines as a hole-injection layer in organic light-emitting diodes (OLEDs). Zhu et al. demonstrated that a SAM of phthalocyanine thiol (HS-Pc) may act as a hole injection material in OLEDs (Fig. 42). The insertion of a SAM of HS-Pc between the Au anode and the hole-transport layers enhances the hole injection, which in-... 

Optical quality coatings of polyaniline have been shown to be effective as hole-injecting materials in polymer light-emitting devices (LEDs), where traditionally indium tin oxide (ITO) has been used. Indeed, these... 

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