Organic light-emitting diodes (OLEDs) with a top-emitting configuration have been widely studied since they can realize high-performance active matrix flat panel display with integration of thin-film transistors within the substrates.Top-emitting OLEDs are generally composed of a reflective bottom anode

organic layers

and a semi-transparent top cathode for light out-coupling.The modification of the bottom anodes is essential for achieving high light-emitting efficiency.Here

efficient top-emitting OLEDs are fabricated with a structure of Al/Ag with O

2

-plasma modification/NPB (35 nm)/Alq

3

(40 nm)/Sm(25 nm)/Alq

3

(50 nm)

where N

N'-di (naphthalene-1-yl)-N

N'-diphenyl-benzidine (NPB) and tris(8-hydroxyquinolinato) aluminum (Alq

3

) are used as a hole-transport layer and an electron-transport/emissive layer

respectively.The metals of silver(Ag) and samarium(Sm) are used as the reflective anode and the semitransparent cathode

respectively.Alayer of Alq

3

overlaid on Sm aims at enhancing light out-coupling efficiency and preventing Sm from oxidation rapidly.The Ag anode is subjected to O

2

-plasma treatment before depositing organic layers.The ultraviolet photoelectron spectroscopy (UPS) analysis shows that the hole injection barrier at Ag/NPB interface is effectively reduced from 1.43 to 1.10 eV by O

2

-plasma treatment.The influence of the O

2

-plasma treatment time on the device performance is also studied.The device performance of the top-emitting OLEDs is remar-kably enhanced by using Ag anode with O

2

-plasma modification.Amaximum current efficiency of 6.14 cd/Ais achieved at an optimal treating time of 60 s.