Light-emitting devices based on ruthenium(II)(4,7-diphenyl-1, 10-phenanthroline)_(3): Device response rate and efficiency by use of tris-(8-hydroxyquinoline) aluminum

摘要

Light-emitting devices based on ruthenium(II)(4,7-diphenyl-1,10-phenanthroline)_(3) (Ru(dphphen)_(3)~(2+)) as emitter have been fabricated. The effect of an electron transport layer of tris-(8-hydroxyquinoline) aluminum (Alq_(3)) on device performance has been investigated. The emission, peaking at 630 nm, for the indium-tin-oxide (ITO)glass/Ru(dphphen)_(3)~(2+)/Ag device reaches maximum luminance after about 15 min at a turn on voltage of 2.5 V. The use of an ITO/Ru(dphphen)_(3)~(2+)/Alq_(3)/Ag device reduces this response time to about 120 s at a turn on voltage of 7 V. A maximum brightness of 1300 cd/m~(2) can be obtained at 15 V within 2 s, with a luminous efficiency of 0.27 cd/A. Based on the charge transporting characteristics of Ru(dphphen)_(3)~(2+) and Alq_(3) films determined by surface photovoltage spectroscopy, the improved device response time and efficiency are attributed to the enhanced electron injection at Ru(dphphen)_(3)~(2+)/Alq_(3) interface.