The enhancement of the luminance efficiency of the top-emitting 2,3-dibutoxy-1,4-polyphenylene vinylene (DB-PPV) polymer light-emitting diodes (PLEDs) with Ca/Ag cathode has been investigated in this work. The luminance efficiency of 2.9 cd A(-1) (at 10 mA) for the thickness of Ca/Ag cathode of 10/15 nm is achieved by our devices. In this paper, partially oxidized CaOx film is proposed to have the capability of hole-blocking as well as the buffer layer on condition of the suitable Ag thickness of Ca/Ag cathode. The tuning ability of colors by simply adjusting the thickness of the DB-PPV emitting layer is available for the devices. (c) 2008 Elsevier B.V. All rights reserved.