High transmittance Er-doped ZnO thin films as electrodes for organic light-emitting diodes

Rare earth element-Erbium (Er) doped ZnO (ErZO) thin films were deposited on glass substrates by pulsed laser deposition (PLD). The effect of the Er doping concentration on photoelectric properties of ErZO thin films was investigated in the range of 0-2.0 wt. %. The Er doping resulted in the improvement of n-type conductivity as compared with intrinsic ZnO thin films. The optimized ErZO thin films present the low resistivity of 3.4 x 10(-4) omega/cm, high carrier concentration of 5.9 x 10(20)/cm(3), and high visible optical transmittance (similar to 93%) when the Er content is 1.0 wt. %. The ErZO thin films were used as transparent anodes to fabricate organic light-emitting diodes (OLEDs). Impressively, with ErZO as the anode, the current efficiency of the OLED device can reach as high as 86.5 cd/A, which was increased by 14% when compared with the reference OLED device (76.0 cd/A) using indium tin oxide as the anode.