The devices show an initial 'settling-in' phase, manifested by an increase of light output which is correlated with an increase in efficiency and voltage. Beyond this 'settling-in' period there are no signs of a degradation in device performance over the operating life. Figure 3 shows a photograph of the EL emission of one of the devices from Fig. 2 taken after ca. 1000 hrs of operation.
Pixel area ca.
238 mm 2 Calcium as cathode is very useful in the study of LEP device performance, polymer batch and encapsulation testing. Such alloy sputter targets can be handled in air and sputtered films are relatively stable. The cathode is a sputtered low work-function Al alloy. The efficiency decays from initially ca. Figure 5 shows the lifetime performance of a device with a similar structure as that for figure 4.