Electron transport silole

Yamaguchi and coworkers [709] have prepared luminescent silole polymers 615a-e. The blue emission of the homopolymers 615a,b can be shifted into the red region by copolymerization with other conjugated units (but for the price of lowered PLQY). Although no device studies have been reported yet, excellent electron-transport properties are expected from such materials [710]. 

As compared with hole-transporting materials, fewer electron-transporting materials have been reported. A well-known green emitter, Alq3, has been used as a good electron transporter. Other reported electron-transporting materials include oxadiazole derivatives, a dendrimer-type oxadiazole, a triazole derivative, tris(phe-nylquinoxaline), silole derivatives, benzimidazole derivative, and boron-containing compounds (Table 7.3). 

We have shown herein several new synthetic methods for the silole-based 7t-conjugated compounds and their possible applications to organic LEDs. The potential of the silole derivatives as new electron-transporting and emissive materials is very high. For their practical application, however, the synthesis of tailor-made silole compounds based on a more precise molecular design would be essential. We are now in a position to access them. 

Silole-containing oligomers have been used as electron transporting layers and as emitters to build efficient OLEDs (Fig. 15) [64, 65]. In OLEDs the performance of 2,5-di(2-pyridyl)-l,l-dimethyl-3,4-diphenylsilacyclopentadiene (PySPy) as electron transport (ET) material was found to be enhanced over Alq3, which is one of the best performing electron transporting materials so far [64], 2,5-Bis-(2, 2"-bipyridin-6-yl)-1,1 -dimethyl-3,4-diphenylsilacyclopentadiene (2PyS2Py),... 

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