Three-Photon Upconversion Luminescence of Gd2O2S: Ho3+, Er3+ for High-Sensitivity FIR Thermometer and Multimode Anti-Counterfeiting

The performance control and multidimensional applications of upconversion phosphor have become the hotspot and difficulty in current research and application due to the complex luminescence mechanism. Based on the efficient Gd2O2S: Er3+ upconversion luminescence of 1550 nm excitation and design strategy for co-doped materials, the multicolor (light green to red) and multifunctional upconversion phosphor Gd2O2S: Er3+, Ho3+ is successfully prepared. Benefiting from the clear mechanism of three-photon upconversion and energy transfer after co-doping, the novel applications of Gd2O2S: Er3+, Ho3+ can greatly be expanded. This phosphor can be well used as a fluorescence thermometer due to the higher sensitivity (2.46% K-1@170 K), wider temperature sensing range (170-267 K, S-r > 1% K-1), and greater color variation (Delta x = 0.2416, Delta y = 0.2483) relative to Gd2O2S: Er3+ and other same type of material. In addition, multiple patterns and encoded outputs are also effectively achieved by the combination of phosphors under multiple light stimuli response. This shows the greater application potential of phosphor in the fields of anti-counterfeiting and information encryption. This study can also provide a new view to study the more high-performance and multifunctional upconversion phosphor.