Developments of Low-driving voltage Organic EL devices by Chemically Doping

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For lowering driving-voltage of organic EL devices, new electron and hole-transporting materials were synthesized and applied to organic EL devices to characterize their EL properties. As for electron-transporting materials, phenanthroline, quinoline and phenyl pyridine derivatives were synthesized and applied to organic EL devices as an electron-transporting layer. The synthesized materials have high glass transition temperatures and showed good uniformity of thin films. The devices used new electron-transporting materials showed lower driving voltage than that of Alq, which have been used for good electron-transporting materials. From these results, Phenanthroline, quinoline and phenylprydine derivatives are expected to be useful as good electron-tranporting materials. Then rare-earth metals were investigated for new chemically doping materials for an electron injection layer. Specifically, Yb showed suitable properties of vacuum deposition and electron-injection ability for Alq, whi … More ch was chemically doping matrix. This result suggests that they will be used for chemically doping materials other than alkaline metals, such as Cs and Li, and expanding a choice of electron injeciton layers for lowering driving-voltage.As for hole-transporting materials, new arylamine origomers having fluorene units were synthesized and applied to organic EL devices. These new oligomers have high glass transition temperatures, and can be formed good thin films by spin-coating and vacuum-evaporation methods. Therefore these oligomers are expected to be useful materials for mass-production and manufacturing of organic EL devices. The devices fabricated by spin-coating were showed lower driving voltage, compared with vacuum-evaporated ones. These results were understood by measurements of hole mobilities by TOF and surface morphology observation by SPM. In addition, these aryamine oligomers formed charge-transfer complex with Lewis acid and an electron-acceptor in solution. Then the films from the solutions showed good hole-injection abilities, and the chemically doping layers achieved lower driving-voltage. Less