Cross Relaxation Channel Tailored Temperature Response in Er³⁺ -rich Upconversion Nanophosphor

Area of Science:

• Materials Science
• Nanotechnology
• Luminescence

Background:

• High doping of lanthanide ions (up to 100%) in nanostructured upconversion (UC) phosphors has been achieved.
• However, this high doping has not led to a corresponding UC enhancement at ambient temperature, limiting applications.

Purpose of the Study:

• To identify the cause of the lack of UC enhancement in highly doped phosphors.
• To quantitatively analyze the roles of different cross-relaxation (CR) channels in UC energy loss.
• To demonstrate a method for enhancing UC luminescence.

Main Methods:

• Utilized an Erbium (Er3+)-rich UC nanosystem as a model.
• Combined theoretical modeling with experimental investigations.
• Investigated the effect of temperature on UC luminescence.
• Fabricated an Er3+-rich core/multi-shell nanophosphor.

Main Results:

• Confirmed that phonon-assisted cross-relaxation (CR) is responsible for the suppressed UC luminescence at ambient temperature.
• Quantitatively revealed the precise roles of various CR channels in UC energy loss.
• Demonstrated that lowering the temperature can enhance UC luminescence by more than two orders of magnitude.

Conclusions:

• Understanding CR mechanisms is crucial for optimizing UC performance in highly doped rare-earth materials.
• The findings pave the way for improved applications of these materials.
• The developed Er3+-rich core/multi-shell nanophosphor shows potential for ultra-sensitive temperature sensing.