Optimized photoluminescence quantum yield in upconversion composites considering the scattering, inner-filter...

Area of Science:

• Materials Science
• Optics
• Nanotechnology

Background:

• Upconversion (UC) composite optimization is complex due to multiple influencing factors.
• Scattering mediums affect dopant excitation and UC efficiency, with implications for thermal effects and saturation.
• Understanding these factors is crucial for reliable UC performance reporting.

Purpose of the Study:

• To investigate the impact of scattering, excitation depth, and sample holder geometry on UC composite performance.
• To quantify the changes in photoluminescence quantum yield (PLQY) under varying conditions.
• To provide insights for optimizing UC composite characterization and maximizing efficiency.

Main Methods:

• Experimental characterization of hexagonal NaYF4:(18%)Yb3+, (2%)Er3+ phosphor.
• Comparison of PLQY in air versus refractive index-matched medium.
• Evaluation of PLQY changes with excitation focal point depth.
• Assessment of self-absorption effects with varying phosphor thickness.
• Comparative analysis of PLQY in cylindrical versus cuboid cuvettes, supported by simulations.

Main Results:

• A 270% PLQY increase was observed in air compared to a refractive index-matched medium.
• Moving the excitation focal point 8.4 mm deep caused a 94% PLQY decrease due to the inner-filter effect.
• Increasing phosphor thickness from 1 to 9 mm reduced PLQY due to self-absorption.
• A cylindrical cuvette yielded a 27% PLQY increase over a cuboid cuvette due to lensing effects.

Conclusions:

• Scattering, inner-filter effects, self-absorption, and cuvette geometry significantly influence UC composite PLQY.
• Optimizing these parameters is essential for maximizing UC efficiency.
• Accurate reporting of UC composite performance necessitates careful consideration of characterization conditions.