Emission enhancement and color modulation of Tm(Ho)/Yb codoped Gd_2(MoO_4)_3 thin films via the use of multilayered structure

The multilayered structure thin films(Gd_2(MoO_4)_3:Ho(Tm)/Yb@Gd_2(MoO_4)_3:Yb)) were prepared through sol-gel and spin-coating method,while the average thinness was nearly 140 nm.We investigated the up-conversion luminescence of Gd2(MoO_4)3:Ho(Tm)/Yb@Gd2(MoO_4)3:Yb thin films,The results show that the double-layer structured thin films are able to increase the emission intensity.The fluorescence enhancement factors of the luminescence from Gd2(MoO_4)3:Ho/Yb@Gd2(MoO_4)3:Yb thin films,located at540 and 662 nm,reach 7.5 and 4.3,respectively.And the enhancement factors of emissions located at450,475 and 650 nm(Gd_2(MoO_4)3:Tm/Yb@Gd_2(MoO_4)_3:Yb)) reach 9,2 and 2,respectively.The considerable enhancement is due to the suppression of surface quenching and energy harvesting via the Yb ions in the outer shell.In addition,the emission color of thin films can be modulated from yellow to blue via tuning the number of Gd2(MoO_4)3:Ho/Yb and Gd2(MoO_4)3:Tm/Yb layers,which provides a feasible strategy to tune the up-conversion emission color.