Structural designing of Zn2SiO4:Mn nanocrystals by co-doping of alkali metal ions in mesoporous silica channels for enhanced emission efficiency with short decay time

Abstract

High purity Zn₂SiO₄:Mn crystals were synthesized by impregnating a precursor solution into mesoporous silica followed by sintering process. The effects of doping alkali metal ions (Li⁺, Na⁺, K⁺) on the structural, morphological and photoluminescence properties were investigated. Formation of single phase α-Zn₂SiO₄:Mn crystals was confirmed from X-ray diffraction. The crystal size was significantly decreased from 54 nm to 35 nm with increasing molar concentration of alkali metal ion dopants in Zn₂SiO₄:Mn. Zn₂SiO₄:Mn crystals co-doped with alkali metal ions showed stronger emission and faster decay times compared to the un-doped Zn₂SiO₄:Mn phosphor. The highest emission quantum yields (EQEs) of 68.3% at λ_exc 254 and 3.8% at λ_exc 425 nm were obtained for the K⁺ ion doped samples with Mn²⁺ : K⁺ ratio of ∼1 : 1. With alkali metal ions (Li⁺, Na⁺, K⁺) co-doping, the decay time of Zn₂SiO₄:Mn crystals was shortened to ∼4 ms, whereas the emission intensity was elevated, with respect to un-doped Zn₂SiO₄:Mn crystals. Zn₂SiO₄:Mn crystal growth in silica pores together with selective doping with alkali metal ions paves a way forward to shorten the phosphor response time, without compromising emission efficiency.