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

High purity ZnSiO: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-ZnSiO: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 ZnSiO:Mn. ZnSiO:Mn crystals co-doped with alkali metal ions showed stronger emission and faster decay times compared to the un-doped ZnSiO:Mn phosphor. The highest emission quantum yields (EQEs) of 68.3% at 254 and 3.8% at 425 nm were obtained for the K ion doped samples with Mn : K ratio of ∼1 : 1. With alkali metal ions (Li, Na, K) co-doping, the decay time of ZnSiO:Mn crystals was shortened to ∼4 ms, whereas the emission intensity was elevated, with respect to un-doped ZnSiO:Mn crystals. ZnSiO: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.