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A thick gold layer is deposited on indium tin oxide (ITO) to improve the interface quality between the ITO anode and the organic layer in organic light-emitting diodes (LEDs). With this improvement, the device with structure ITO/Au/hole-transport-layer(HTL)/poly(p-phenylenevinylene)/Ca/Ag, achieved a lower turn-on voltage from 4 V to about 1.6 V and an increase in luminescence intensity by more than a factor of two at the same voltage. The work function of the Au facilitates the formation of an ohmic contact and good mechanical adhesion to the HTL. The experimental results suggest that the ITO contact limits the supply of current for radiative recombination. The improvement of the device performance is due to the smoother Au surface and the matching of the Au work function with the highest occupied molecular orbital level of adjacent HTL layer.
Date of Publication: March 2005