有機EL素子における電気伝導の温度特性とキャリア挙動

抄録

Organic Electroluminescent device (OLED) was fabricated using a vacuum evaporation method and thermal properties were investigated. The OLED has an Indium Tin Oxide (ITO)/ N,N'-diphenyl-N,N'- bis(3-methylphenyl) 1- 1'biphenyl- 4,4'-diamine (TPD)/ tris- (8-hydroxyquinoline) aluminum (Alq)/ Lithium fluoride (LiF)/ aluminum (Al) structure. An electron dominant device of an Al/ Alq/ LiF/ Al structure, or a hole dominant device of an ITO/ TPD/ Al structure was also fabricated in order to study the carrier behavior in the OLEDs. The current density vs. voltage (J-V) properties with various thickness of organic layers were investigated in the both electron and hole dominant devices, and the thermal dependence of J-V properties was observed in the devices. At room temperature, conductions in large current region were considered to be due to space-charge-limited current for all the devices. Especially, for the Al/ Alq/ LiF/ Al device and the OLED, J∝V^m+1 relationships were observed across wide current region. At low temperature, tunnel currents were estimated for the ITO/TPD/Al device. For the Al/ Alq/ LiF/ Al device and the OLED, J∝V^m+1 relationships were observed across wide current region at low temperature.