Al2O3/TiO2 multilayer thin films grown by plasma enhanced atomic layer deposition for organic light-emitting diode passivation

Aluminum oxide (Al2O3) and titanium dioxide (TiO2) films deposited on flexible polyethersulfone substrates by plasma-enhanced atomic layer deposition have been investigated for transparent barrier applications. The effects of the induced plasma power on the passivation properties were investigated as function of film thickness and substrate temperature. The optimum plasma power and substrate temperature were investigated through measurements of the refractive index and packing density of the Al2O3 and TiO2 films. In this research, three different barrier structures were investigated for the purpose of improving water vapor barrier characteristics. A low water vapor transmission rate of approximately 5 × 10− 3 g/m2·day or below was achieved with two pairs of Al2O3/TiO2 stacks with a total stack thickness of 40 nm deposited at 80 °C. The passivation performance of the multilayer film was investigated using an organic light-emitting diode. The coated device lifetime was 267 h, which was 41 times longer than that of an uncoated sample.