Photoluminescence properties and efficient energy transfer of Ce3+/Eu2+ activated K2Ba7Si16O40 phosphors

Abstract

Ce3+/Eu2+ activated K2Ba7Si16O40 phosphors have been synthesized via a high-temperature solid-state method with CO atmosphere. Under ultraviolet (UV) light pump, the photoluminescence (PL) spectra of K2Ba7Si16O40: Ce3+ is composed of a broadband from 300 nm to 500 nm ascribed to the spin-allowed 5d–4f transition of Ce3+ ions. The optimal concentration is 8% for Ce3+ single doped K2Ba7Si16O40 due to the ernergy dispersion between Ce3+ ions and the critical distance between Ce3+ ions is 15.05 Å. K2Ba7Si16O40: Eu2+ emits a broad green emission peaking at 498 nm. The spectral overlap between the emission of Ce3+ and the excitation of Eu2+ suggests the resonance-type energy transfer from Ce3+ to Eu2+, which is further demonstrated by the decay curves of K2Ba7Si16O40: 8 mol% Ce3+, m Eu2+. The critical distance between Ce3+ and Eu2+ ions is calculated to be 25.06 Å by Dexter’s theory. Furthermore, the energy transfer mechanism is dipole-dipole interaction. In addition, the thermal activation energy is calculated to be 0.26 eV. The CIE coordinates can be tuned from blue to green by increasing Eu2+ ions. All results suggest that K2Ba7Si16O40: Ce3+, Eu2+ is potentially useful for near-UV pumped white LEDs.