The Hybrid Thin Film Encapsulation Method Based On ALD And MLD

Organic light emitting diode(OLED) possess many advantages such as: selfluminous, high brightness, high contrast ratio, fast response and flexibility, etc.They have many applications in lighting and display area in the future. However, there are still some challenges for the development of OLED. The main problem is to solve the degradation of OLED when exposed to humidity and oxygen in environment. In order to overcome this issue, thin film encapsulation(TFE) as an effective method to avoid water vapor permeation has been studied.This paper aim to improve the gas barrier properties of TFE, a hybrid encapsulation method based on atomic layer deposition(ALD) and molecular layer deposition(MLD) has been proposed. Hybrid Organic/inorganic nanolaminates with high barrier performance against water vapor were fabricated under a low temperature of 80℃.By optimizing the oxidant precursor and thickness of the laminates, the film quality has been improved and lifetime of the encapsulated OLED has been prolonged.First, this paper gave a brief introduction on the basic structure and luminous mechanism of OLED. Then, the degradation process has been analyzed and encapsulation technique have been put forward. Under the deposition temperature of 80℃,Trinethyluminium(TMA) and different oxidant precursor(H2O or O3) were adopted for fabricating inorganic thin film Al2O3.Besides, TMA and ethylene glycol(EG) were selected for the organic thin film alucone. Comparing with the surface topography and electrical properties of different thin films, those fabricated based on O3 oxidant have less reaction time and surface roughness. Lifetime of the encapsulated OLED based on O3 were 2 times longer than those based on H2 O.To further improve the barrier properties and verify the encapsulation performance of the flexible hybrid films, we used PET as substrate and insert alucone organic layer(4nm) into Al2O3 inorganic layer at the deposition temperature of 80℃. Compared with the single inorganic thin films under the same thickness, after the bending test, it was found that the dispersion of organic layer is beneficial for keeping flat surface morphology and better barrier characteristics. The lowest WVTR value we obtained after the bending test was 7.110-5g/m2/day. Through the optical transmittance test, this flexible hybrid thin films achieved high transmittance value of 69% in the visible range. We believe this hybrid ALD/MLD TFE will be a potential candidate for the usage for the flexible OLED...