A thin-film electroluminescent device (ELD) has been fabricated by incorporating multi-barrier layers into the ZnS:Mn phosphor using r.f. magnetron sputtering. The number (N) of intermediate barriers ( = 10 nm) was found to have a large effect on the device performance. The improvement in crystallinity of the phosphor layer can be explained by the extra thermal-cycle annealing due to the different deposition temperatures for Y2O3 (50°C) and ZnSr:Mn (300°C). As the number of the Y2O3 barrier layer increases from N = 0 to N = 3, the ELD shows a threefold increase in brightness and the threshold voltage decreases from 93.6 to 60.7 V. The result of Sawyer-Tower circuit measurement confirms that the transferred charge increases with the number of intermediate barriers. However, further increasing the intermediate barriers (N > 3) leads to a degraded ELD performance. The results are discussed in terms of the contributions of the crystallinity, interface state, electron tunneling, and field redistribution of active layer as the mechanisms responsible for the performance of ELD with the multi-barrier insulators structure.
- Barrier layer
- Electroluminescent device