Multilayer organic electroluminescent devices (OELDs) were fabricated with
highly pure 2-(2-hydroxyphenyl)benzoxazolato lithium (LiPBO), which was obt
ained through stepwise purification process, as a blue emission layer. The
ionization potential of the carefully purified LiPBO was similar to5.82 eV.
The multilayer OELD with a hole-blocking layer (HBL) emitted almost pure b
lue light with the CIE color coordinate of x=0.15 and y=0.08. However, the
emission color was redshifted when an electron-transporting layer (ETL) was
introduced instead of the HBL. The device with both the HBL and the ETL sh
owed stable and bright blue emission above 14 000 cd/m(2) with the color co
ordinate of x=0.15 and y=0.11, even though the color purity was slightly po
orer than that with only the HBL. (C) 2001 American Institute of Physics.