Effect of transparent film desiccant on the lifetime of top-emitting active matrix organic light emitting diodes

The effects of a transparent film desiccant on the lifetime of top-emitting active matrix organic light emitting diodes (AMOLEDs) were investigated. The transparent film desiccants were prepared by mixing solutions dispersed with calcium oxide powders and ultraviolet-curable resins. As the solid content in the solutions increased from 15 to 30 wt %, the average particle size increased from 107 to 240 nm, whereas the transmittance of the films decreased from 98% to 80% in the visible range. The devices encapsulated with the transparent film desiccants which contained 20 wt % CaO exhibited no dark spots and 97% of the initial luminance, even after being stored for over 500 h at 70 degrees C and 90% relative humidity. Also, the operational lifetime of these devices was 1850 h, ten times longer than that of a device without desiccant. These results confirmed that the transparent film desiccants, which absorbed the moisture that penetrated into the devices, could be applied to the encapsulation of top-emitting AMOLEDs. (c) 2007 American Institute of Physics.