Characterization of thin-film electroluminescent devices with multiple Ta₂O₅ interlayers incorporated into SrS:Pr,Ce phosphor

A thin-film electroluminescent device (ELD) has been fabricated by incorporating multiple Ta₂O₅ interlayers into the SrS:Pr,Ce phosphor layer using rf-magnetron sputtering. X-ray measurement results confirm the enhanced crystallinity of the phosphor layer and can be explained by the extra thermal-cycle annealing due to the different deposition temperatures for Ta₂O₅ (100°C) and SrS (500°C). The inclusion of thin barrier films is expected to redistribute the internal field and introduce additional interface states in the ELD structure. Based on the results of Sawyer-Tower circuit measurements, it is found that the transferred charge density in the active layer can increase with the number of intermediate layers. This contributes to an increase in brightness and the reduction of the threshold voltage. Moreover, a stacked structure for SrS:Pr and SrS:Ce phosphor layers with window effects is proposed to alleviate the absorption problem in the SrS:Pr,Ce multi-barrier ELD structure. Details of the mechanism and the improvement in the chromaticity will also be described.