Multi-photon up-conversion enhancement from Gd₂(MoO₄)₃:Er/Yb thin film via the use of sandwich structure

Lanthanide-doped up-converting nano-particles reveal significant promise for data storage, biological imaging, and temperature sensing, but have not been extensively used due to their low emission intensity. Here, we investigate the up-conversion emissions of Gd₂(MoO₄)₃:Er/Yb thin films that are sandwiched by Gd₂(MoO₄)₃:Yb thin films. Our results show that the sandwiched thin films possess significant enhancement of emission intensities. The enhancement factors of the green and red emissions, radiated from Gd₂(MoO₄)₃:Er/Yb films, reach 9.5 and 5, respectively. Moreover, the ability of sandwich structured thin films in multi-photon up-conversion enhancement is more excellent than that of laser power, attributed to the suppression of undesired radiative/non-radiative recombination of the intermediate states. In addition, the intensity-based temperature absolutely sensitivity of sandwich structured Gd₂(MoO₄)₃:Er³⁺/Yb³⁺ reaches 0.013 K⁻¹ at 498 K, which indicate this sandwich structured thin films have larger potential in thermal sensors. This sandwich structure might extend the applications of Ln³⁺-doped materials in super-resolution imaging and temperature sensing.