Method for Aluminum Oxide Thin Films Prepared through Low Temperature Atomic Layer Deposition for Encapsulating Organic Electroluminescent Devices

Abstract

Preparation of dense alumina (Al2O3) thin film through atomic layer deposition (ALD) provides a pathway to achieve the encapsulation of organic light emitting devices (OLED). Unlike traditional ALD which is usually executed at higher reaction n temperatures that may affect the performance of OLED, this application discusses the development on preparation of ALD thin film at a low temperature. One concern of ALD is the suppressing effect of ambient temperature on uniformity of thin film. To mitigate this issue, the pumping time in each reaction cycle was increased during the preparation process, which removed reaction byproducts and inhibited the formation of vacancies. As a result, the obtained thin film had both high uniformity and density properties, which provided an excellent encapsulation performance. The results from microstructure morphology analysis, water vapor transmission rate, and lifetime test showed that the difference in uniformity between thin films prepared at low temperatures, with increased pumping time, and high temperatures was small and there was no obvious influence of increased pumping time on light emitting performance. Meanwhile, the permeability for water vapor of the thin film prepared at a low temperature was found to reach as low as 1.5 × 10 −4 g/(m 2 · day) under ambient conditions of 25 °C and 60% relative humidity, indicating a potential extension in the lifetime for the OLED.

Thin Film Encapsulation at Low Temperature Using Combination of Inorganic Dyad Layers and Spray Coated Organic Layer

“…Recently, there has been much advancement related to thin film encapsulation. Thin film barriers are either produced using high quality inorganic layer or alternate layers of organic-inorganic layers [4]. These barriers are better because it can be used on flexible devices and does not require sealant at the edges.…”

Self-powered, ultraflexible photonic skin for continuous bio-signal detection via air-operation-stable polymer light-emitting diodes

“…The operational lifetime and turn-on voltage of the inverted PLED with PEIE:Liq and SY were compared to those in previous studies (Fig. 2b) [28,[33][34][35][36][37][38][39][40][41][42][43][44][45]. The inverted PLED has an excellent half luminance lifetime of 41.5 h with 8-V operation in ambient air without encapsulation, while maintaining a low turn-on voltage (4.7 V).…”

Self-powered ultraflexible photonic skin for continuous bio-signal detection via air-operation-stable polymer light-emitting diodes

“…The operational lifetime and turn-on voltage of the inverted PLED with PEIE:Liq and SY were compared to those in previous studies (Fig. 2b) 28,[33][34][35][36][37][38][39][40][41][42][43][44][45] . The inverted PLED has an excellent half luminance lifetime of 41.5 h with 8-V operation in ambient air without encapsulation, while maintaining a low turnon voltage (4.7 V).…”