A spectroscopic study on SrS : Cu,Ag two-component electroluminescent phosphors

Under 4.507 eV excitation, the SrS : Cu,Ag thin "lms exhibited a saturated blue emission at 2.876 eV at room temperature and two additional emission bands at 3.443 and 2.398 eV were also observed at 10 K. By comparing with singly doped SrS : Cu and SrS : Ag, the two bands at 3.443 and 2.876 eV were assigned to the Ag emission bands and the 2.398 eV band to Cu emission. The enhancement of the 2.876 eV Ag emission band and the simultaneous suppression of the 2.398 eV Cu emission band are indicative of the presence of strong energy transfer from Cu to Ag ions in SrS : Cu,Ag. Low-temperature PLE spectrum of the 2.876 eV emission band was found to exhibit Cu excitation bands, con"rming the presence of energy transfer from Cu to Ag. However, the energy transfer process from Cu to Ag exhibited anomalous properties that cannot be explained by the standard energy transfer theory. Therefore, instead of a Dexter-type energy transfer, electron transport was proposed as a possible coupling mechanism between the Cu and Ag ions in SrS. ( 2000 Elsevier Science B.V. All rights reserved.