$MoOx$ modified Ag anode for top-emitting organic light-emitting devices

Efficient top-emitting organic light-emitting devices (TOLEDs) using a thin $MoOx$ layer modified Ag as the effective hole-injection anode are demonstrated. With tris-(8-hydroxy quinoline)aluminum as emitting layer and trilayer $LiF∕Al∕Ag$ as semitransparent cathode, the $Ag∕MoOx$ based TOLED shows a tune-on voltage of $2.67V$ and a maximum current efficiency of $7.27cd∕A$⁠, which are much better than those (⁠$3.92V$⁠, $6.12cd∕A$⁠) obtained from $Ag∕Ag2O$ based TOLED and those (⁠$5.25V$⁠, $3.5cd∕A$⁠) obtained from the corresponding bottom-emitting organic light-emitting devices. Contact potential difference measurement shows that the work function of $Ag∕MoOx$ is higher than those of $Ag∕Ag2O$ and ozone-treated indium tin oxide, leading to a stronger hole injection. The good performance of $Ag∕MoOx$ based TOLED is attributed to the efficient hole injection from the $Ag∕MoOx$ anode as well as a microcavity effect.