Space charge and light generation in SrS:Ce thin filmelectroluminescent devices

Transient light and charge-voltage measurements on SrS and SrS:Ce thin film electroluminescent devices have been carried out with triangular voltage bursts after illumination. The observations indicate that the trailing edge emission is due to electrons which are emitted from the anodic interface as soon as the field there changes sign and recombine effectively with ionized Ce atoms. From charge-voltage measurements the space charge in the phosphor layer is estimated to be two times higher for the Ce doped sample. Due to this sample charge the field in the phosphor layer of the SrS:Ce devices decreases dramatically from the cathodic toward the anodic interface. If the field at the anodic interface is close to zero, efficient light emission will arise from recombination of electrons with ionized Ce atoms in this region