Vanadium-doped indium tin oxide as hole-injection layer in organic light-emitting devices

Abstract

Organic light-emitting devices were fabricated by using vanadium-doped indium tin oxide (ITO) as the hole-injection layers between the hole transport layer, N,N-'-dia(1-napthl)-N,N-'-diphenyl benzidine and the ITO anode. The vanadium-doped ITO layer was 15-nm thick with three different vanadium concentrations (6, 10.5, and 12.5 mol %). Three different resistivities (10, 500, and 10 000 Omega cm) and work functions (5, 5.2, and 5.4 eV) were obtained. The device with 6 mol % V-doped ITO layer possessing the least resistivity (10 Omega cm) and work function (5 eV) has the lowest turn-on voltage (below 3 V), the lowest operating voltage (below 7 V), the highest luminance (1000 cd/m(2) below 7 V), and the highest power efficiency (>5 1m/W at 10 mA/cm(2)) among all. Such performance was attributed to the balance between the carrier concentration and the energy barrier for the hole injection.