Design principles for (efficient) excited-state absorption-based blue-to-UV upconversion phosphors with Pr³.

Area of Science:

• Materials Science
• Solid-State Chemistry
• Photonics

Background:

• Current UV light generation methods are inefficient, costly, and often use toxic mercury.
• Blue light-emitting diodes (LEDs) offer a sustainable and cost-effective alternative for light generation.
• Upconversion (UC) schemes can convert lower-energy light to higher-energy UV light.

Purpose of the Study:

• To investigate the potential of Pr3+ ions for blue-to-UV light upconversion.
• To identify host materials that optimize the upconversion efficiency for Pr3+.
• To understand the relationship between host properties and excited-state dynamics for efficient UC.

Main Methods:

• Synthesis and activation of various host materials (halidoelpasolites, oxyfluorides, garnets, silicates, borates) with Pr3+.
• Quantum yield measurements under blue light excitation.
• Steady-state, time-resolved, and temperature-dependent luminescence spectroscopy.

Main Results:

• Pr3+ ions can achieve blue-to-UV upconversion via excited-state absorption (ESA).
• Efficient UC requires a long decay time of the intermediate 3P0 level and limited non-radiative crossover from 4f15d1 states.
• Cs2NaYCl6:Pr3+ exhibited the highest upconversion quantum yield (0.11%) among tested materials, surpassing established standards like LuAG:Pr3+ and YPS:Pr3+.

Conclusions:

• Cs2NaYCl6:Pr3+ is a highly efficient material for blue-to-UV upconversion due to its low phonon energy and rigid structure.
• Careful matching of host material properties is crucial for optimizing ESA-based UC efficiency.
• This research provides guidelines for developing sustainable UV light sources.