Engineering a novel role for Yb3+ to overcome thermal quenching and improve photothermal conversion efficiency as well as temperature sensing performance.

In this paper, two types of phosphors, Cs 3 GdGe 3 O 9 :Er3+ and Cs 3 GdGe 3 O 9 :Yb3+/Er3+, were synthesized using the high-temperature solid-state method, and a new role for Yb3+ was successfully achieved. The presence of low phonon energy in the matrix and the low energy level mismatch between the 2F 5/2 and the 4I 11/2 enables the construction of a phonon-assisted channel between Yb3+ and Er3+ through doping with Yb3+ ions. This channel overcomes thermal quenching and achieves thermal enhancement at high temperatures. Additionally, Yb3+ increases the chance of non-radiative transition within the matrix, effectively converting the 980 nm laser into heat energy. This leads to a significant change in the surface temperature of the sample, greatly improving the photothermal conversion efficiency. Moreover, Yb3+ greatly enhances the emission intensity of green light, resulting in a maximum relative sensitivity of 1.11 % K−1 for temperature measurements in the Er3+ single-doped system and 1.28 % K−1 in the Yb3+/Er3+ co-doped system, based on the Er3+ thermally coupled energy level. These results demonstrate that this paper provides a new idea for materials to overcome thermal quenching and improve the efficiency of photothermal conversion and temperature sensing performance. The novel role of Yb3+ has been intensively investigated in Cs 3 GdGe 3 O 9 , where Yb3+ can act as a phonon-assisted channel linker for thermal enhancement, as a heat collector of importance for photothermal therapy, and to improve the performance of temperature measurements based on the thermal coupling energy level of Er3+. [Display omitted] • Other novel roles for Yb3+ are explored for the first time. • Enables thermal enhancement at high temperatures, providing a novel strategy for overcoming thermal quenching. • The photothermal conversion efficiency of the sample is improved by Yb3+, which is important for photothermal therapy. • Improved temperature measurement performance based on Er3+ thermally coupled energy levels. [ABSTRACT FROM AUTHOR]