Organic EL device using SrOx as an electron injection material

Abstract

AbstractStrontium oxide (SrOx) is known as an alkaline‐earth metal oxide that has a low work function. We have prepared an organic EL device with an ITO/PVCz (polyvinylcarbazole)/Alq/SrOx/Al structure. SrOx was stacked as an electron injection layer on the Alq (aluminum quinolinol complex) emission layer by means of a reactive vapor deposition method by evaporating metallic strontium under an oxygen atmosphere. By inserting the SrOx film of less than 5 nm in thickness, significant improvements were achieved in the device properties, including luminance, lifetime, threshold voltage, and efficiency. XPS measurement and AFM analysis showed that the film morphology of the SrOx layer had an island structure. The oxidation of SrOx was enhanced by setting the oxygen partial pressure for the reactive vapor deposition to 10−3 to 10−2 Pa, which yielded the optimum EL properties. © 2003 Wiley Periodicals, Inc. Electron Comm Jpn Pt 2, 86(7): 73–80, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjb.1126