DC lifetime of encapsulated organic light emitting diodes

Organic light emitting diodes (OLEDs) are ideal sources for chemical and biological optical sensors [1], due to their simplicity, low cost (disposable applications) and possibility to be integrated on chip and fabricated in the form of large 2D arrays (microarray fluorescence [2]) even on flexible plastic substrates. OLEDs with lifetimes of a few hundreds of hours at initial luminance values in the range (500÷1000) cd/m 2 are suitable for the above applications, but these lifetimes can be achieved only by a proper encapsulation. Fast, simple and inexpensive encapsulation methods are highly desirable to keep the low cost profile and for this reason we report two different encapsulation structures and compare their effectiveness in increasing device lifetime of bilayer green emitting OLEDs based on Tris (8 idroxyquinoline) aluminum (Alq3) as emitting material.