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 inc orporating multiple Ta2O5 interlayers into the SrS:Pr,Ce phosphor laye r 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 temp eratures for Ta2O5 (100 degrees C) and SrS (500 degrees C). The inclus ion of thin barrier alms is expected to redistribute the internal fiel d and introduce additional interface states in the ELD structure. Base d on the results of Sawyer-Tower circuit measurements, it is found tha t 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 st acked structure for SrS:Pr and SrS:Ce phosphor layers with window effe cts is proposed to alleviate the absorption problem in the SrS:Pr,Ce m ulti-barrier ELD structure. Details of the mechanism and the improveme nt in the chromaticity will also be described.