Crucial processes for upconversion white emission and ultrahigh sensitivity in Er3+/Tm3+/Yb3+ tri-doped double perovskite Gd2ZnTiO6 phosphors

Abstract

Upconversion (UC) luminescence properties are of great significance in realizing good performances on practical display and sensing applications and that can be tuned by adjusting UC energy transfer (ET) processes. In this work, we devoted to gaining UC white emission and achieving high sensing sensitivity by manipulating ET processes in the Er3+/Tm3+/Yb3+ tri-doped double perovskite Gd2ZnTiO6 (GZT) phosphors. Nearly standard UC white emission with the CIE coordinate of (0.333, 0.331) was obtained based on effective ET processes between Er3+, Tm3+ and Yb3+ in the GZT: 0.5%Er3+/3.5%Tm3+/15%Yb3+ sample. The maximum absolute sensitivity of 5.02 K-1 (473 K) of non-thermally coupled levels (I635−685∕I500−540) and another the maximum absolute sensitivity of 84.6 × 10−4 K−1 (473 K) of thermally coupled levels (I500−540∕I540−600) were gained. The two absolute sensitivities both are higher than that in Tm3+/Yb3+ and Er3+/Yb3+ co-doped double perovskite GZT phosphors, respectively. The enhancements of sensitivities are due to the effective ET processes between Er3+, Tm3+ and Yb3+. This work reveals not only certified UC processes for UC white emission but also a valid idea on the manipulation of UC processes towards high absolute sensitivity in phosphors.