Conceptual Ultraviolet‐C Light Source Based on Up‐Conversion Luminescence

Molten Salt Synthesized CaTa4O11:Er3+/Yb3+ with Superior Upconversion Luminescence

“…The upconversion luminescence (UCL) process is the conversion of low energy photons to high energy photons via multiphoton absorptions. Due to this special property, UCL phosphors now have been used in a wide range of fields, including anticounterfeiting labeling, biological imaging, medical probes, solar cells, solid-state lasers, sterilization, etc. − At present, β-NaYF 4 :Er 3+ /Yb 3+ is the most widely studied and applied phosphor which demonstrates the highest UCL intensity. , However, fluorides in general have relatively poor chemical stability and cannot be used for long time in some special occasions such as high temperature and acid and alkali environments. , Therefore, it is necessary to explore oxide-based hosts with high UCL efficiency to replace fluoride counterparts due to their high thermal and chemical stabilities and low or even no toxicity. , However, this is a tough challenge because oxides have relatively high phonon energy compared to fluoride hosts, and hence, most oxide-based phosphors have low UCL emission intensity. While looking for oxide matrices with low phonon energy, it is also necessary to improve energy transfer efficiency of Yb 3+ to Er 3+ from the perspective of Yb 3+ and Er 3+ -codoped oxide-based UCL phosphors.…”

Abnormal upconversion luminescence induced by defects and Er3+–Yb3+ distance change in Cs3GdGe3O9:Er3+/Yb3+ phosphors

“…Upconversion luminescence (UCL) is a photoluminescence process in which materials absorb multiple low‐energy photons and emit a high‐energy photon, which can transform infrared light to visible light and ultraviolet light 1 . Because of this property, UCL materials are widely used in many fields, including photothermal sensing, 2,3 anti‐counterfeit labels, 4,5 solar cells, 6,7 bioimaging, 8,9 plant growth, 10,11 and surface decontamination 12 . It is well known that the phenomenon of thermal quenching is ubiquitous in photoluminescence phosphors, that is, the luminescence intensity decreases sharply with increasing temperature, which is due to the non‐radiative transition of multiple phonons.…”

“…1 Because of this property, UCL materials are widely used in many fields, including photothermal sensing, 2,3 anti-counterfeit labels, 4,5 solar cells, 6,7 bioimaging, 8,9 plant growth, 10,11 and surface decontamination. 12 It is well known that the phenomenon of thermal quenching is ubiquitous in photoluminescence phosphors, that is, the luminescence intensity decreases sharply with increasing temperature, which is due to the non-radiative transition of multiple phonons. This thermal quenching restricts their practical application fields in hightemperature environment.…”