Low Temperature DC Sputtering Deposition on Indium-Tin Oxide Film and Its Application to Inverted Top-emitting Organic Light-emitting Diodes

Indium tin oxide (ITO) ultrathin films were prepared on glass substrate by DC (direct current) magnetron sputtering technique with the assistance of H2O vapor to avoid potential surface damage. The film properties were characterized by X-ray diffraction (XRD) technique, four-point probe method and spectrophotometer. The results show that the deposited ITO film with introduced H20 during sputtering process was almost amor- phous. The average visible light transmission of 100 nm ITO film was around 85% and square resistivity was below 80 Ω/square. The film was used as the transparent anode to fabricate an inverted top-emitting organic light-emitting diodes (IT-OLEDs) with the structure of glass substrate/AIq3 (40 nm)/NPB (15 nm)/CuPc(x nm)/ITO anode (100 nm), where the film thickness of CuPc was optimized. It was found that the lumi-nance of this IT-OLEDs was improved from 25 cd/m2 to more than 527 cd/m2 by increasing the thickness of CuPc, and luminance efficiency of 0.24 lm/W at 100 cd/m2 was obtained, which indicated that the optimized thickness of CuPc layer was around 15 nm.