Low-temperature gas-barrier films by atomic layer deposition for encapsulating organic light-emitting diodes

Abstract

Dependences of gas-barrier performance on the deposition temperature of atomic-layer-deposited (ALD) Al₂O₃, HfO₂, and ZnO films were studied to establish low-temperature ALD processes for encapsulating organic light-emitting diodes (OLEDs). By identifying and controlling the key factors, i.e. using H₂O₂ as an oxidant, laminating Al₂O₃ with HfO₂ or ZnO layers into AHO or AZO nanolaminates, and extending purge steps, OLED-acceptable gas-barrier performance (water vapor transmission rates ∼ 10^-6 g m^-2 d^-1) was achieved for the first time at a low deposition temperature of 50 °C in a thermal ALD mode. The compatibility of the low-temperature ALD process with OLEDs was confirmed by applying the process to encapsulate different types of OLED devices, which were degradation-free upon encapsulation and showed adequate lifetime during accelerated aging tests (pixel shrinkage <5% after 240 h at 60 °C/90% RH).