Abstract
Various encapsulated films for flexible organic light emitting diodes (OLEDs) were studied in this work, where gas barrier layers including inorganic Al2O3 thin films prepared by atomic layer deposition, organic Parylene C thin films prepared by chemical vapor deposition, and their combination were considered. The transmittance and water vapor transmission rate of the various organic and inorgabic encapsulated films were tested. The effects of the encapsulated films on the luminance and current density of the OLEDs were discussed, and the life time experiments of the OLEDs with these encapsulated films were also conducted. The results showed that the transmittance are acceptable even the PET substrate were coated two Al2O3 and Parylene C layers. The results also indicated the WVTR of the PET substrate improved by coating the barrier layers. In the encapsulation performance, it indicates the OLED with Al2O3 /PET, 1 pair/PET, and 2 pairs/PET presents similarly higher luminance than the other two cases. Although the 1 pair/PET encapsulation behaves a litter better luminance than the 2 pairs/PET encapsulation, the 2 pairs/PET encapsulation has much better life time. The OLED with 2 pairs/PET encapsulation behaves near double life time to the 1 pair encapsulation, and four times to none encapsulation.
Highlights
Due to the simplicity, organic light emitting diodes (OLEDs) can be built on glass substrates and flexible substrates
To prevent the penetration of water vapor into the OLEDs, various encapsulated films for flexible OLEDs were studied, where gas barrier layers including inorganic Al2O3 thin films prepared by atomic layer a Corresponding author: author@e-mail.org deposition, organic Parylene C thin films prepared by chemical vapor deposition, and their combination were considered
The OLED with 2 pairs/PET encapsulation behave near double life time to the 1 pair encapsulation
Summary
Organic light emitting diodes (OLEDs) can be built on glass substrates and flexible substrates. It is distributed to the penetration of oxygen and water vapor to the organic layers through the substrate and the encapsulated film [13]. The polymer substrates are the most promising candidate for the flexible encapsulation. The water vapor transmission rate (WVTR) of the polymer substrate is substantially below the requirement of OLED encapsulation. Polymer substrates coated barrier thin films to improve the WVTR are essential for flexible OLED encapsulation [4, 5]. Inorganic thin films have shown the potential to be the barrier layer for flexible OLED encapsulation [6]. These inorganic thin films have low WVTR, the defects of pinholes cannot be avoided because of the limitation of the vacuum deposition process. An organicinorganic multi-barrier become an alternative to prevent the defects. [7-11]
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