An efficient top-emitting electroluminescent device on metal-laminated plastic substrate
- PDF / 99,242 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 105 Downloads / 125 Views
DD11.12.1
An efficient top-emitting electroluminescent device on metal-laminated plastic substrate L.W.Tan, X.T.Hao, K.S.Ong, Y.Q Li, and F.R. Zhu* Institute of Materials Research and Engineering, No.3 Research Link Singapore, 117602 ABSTRACT An efficient flexible top-emitting organic light-emitting device (OLED) was fabricated on an aluminum-laminated polyethylene terephthalate substrate. A spin-coated light-emitting polymer layer was sandwiched between a silver anode and a multi-layered semitransparent cathode. The performance of polymer OLEDs was analyzed and compared with that of the devices having a conventional structure. An optical microcavity formed in the device enables to tune the emission color by varying the thickness of the active polymer layer. The OLEDs having a 110-nm-thick active polymer layer exhibited superior electroluminescence performance, with a turn-on voltage of 2.5V and a luminance efficiency of 4.56 cd/A at an operating voltage of 10V. INTRODUCTION Organic light emitting devices (OLEDs) have recently attracted attention as display devices that can replace liquid crystal displays because OLEDs can produce high visibility by selfluminescence and they can be fabricated into lightweight, thin and flexible displays1-4. The conventional structure of OLEDs consists of a metal or metal alloy cathode and a transparent anode on a transparent substrate, whereby light can be emitted from the transparent substrate. The OLEDs may also have a top-emitting structure that has a relatively transparent top electrode so that light can emit from the side of the top electrode, which can be formed on either an opaque or a transparent substrate5-7. The top-emitting OLED structures increase the flexibility of device integration and engineering and are desirable for high-resolution active matrix displays. OLEDs have usually been built on rigid glass substrates due to their low permeability to oxygen and moisture. Over the past few years, ultrathin glass sheets8-10 and transparent plastic substrates11, 12 have been considered as the possible substrate choices for flexible OLEDs. Ultrathin glass sheets, however, are very brittle and OLEDs formed on ultrathin glass sheets have limited potential as flexible OLED displays. To make OLEDs that are lighter, thinner, more rugged and highly flexible, plastic substrates, e.g. polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), have been used for flexible OLEDs. It is apparent that PET, PEN and other commonly used plastic foils do not have sufficiently high impermeability for OLEDs. Accordingly, efforts have been made to develop highly effective barrier against oxygen and moisture permeation and hence to minimize degradation of the devices on plastic substrates13. Multilayer barrier approaches have been used to improve the barrier property of plastic substrates, such as using alternative multi-layers of organic-inorganic structures, incorporation of getter materials, thick capping metals, pinholes reduction, etc. Further optimization is required to avoid the
Data Loading...
