Highly efficient organic light-emitting devices with surface-modified metal anode by vanadium pentoxide

An Au film modified by vanadium pentoxide (V₂O₅) has been investigated as the anode for injecting holes in organic light-emitting devices (OLEDs). It is found that OLEDs with the V₂O₅ modified Au anode have much lower driving voltages and much higher current efficiencies (four times higher) as compared with the OLEDs with bare Au as anode. The results of ultraviolet photoelectron spectroscopy and UV–visible spectrometer analysis indicate that the Au anode treated by V₂O₅ has a smaller barrier height and thus facilitates hole injection, apart from a high optical transparency of Au/V₂O₅. For the OLEDs with Au/V₂O₅ anode, the driving voltage is decreased by 13 V and the maximum current efficiency (4.1 cd A⁻¹) is four times higher as compared with that of the bare Au anode device (∼0.9 cd A⁻¹). The OLEDs with Au/V₂O₅ anode also have about 1.4 times higher efficiency than that of the OLEDs (∼2.8 cd A⁻¹) with ITO/V₂O₅ anode.