Halide Double Perovskite Nanocrystals Doped with Rare-Earth Ions for Multifunctional Applications

Area of Science:

• Materials Science
• Nanotechnology
• Solid-State Chemistry

Background:

• Lead-free halide double perovskites often have low photoluminescence quantum yield (PLQY) due to indirect bandgaps.
• Doping is a key strategy to enhance optical properties in these materials.

Purpose of the Study:

• To develop efficient blue-emitting Sb³⁺-doped Cs₂NaInCl₆ nanocrystals (NCs) for advanced optical applications.
• To investigate the impact of rare-earth (RE) ion doping on the PLQY and defect compensation in these NCs.

Main Methods:

• Synthesis of Sb³⁺-doped Cs₂NaInCl₆ NCs and subsequent doping with RE ions (Sm³⁺, Eu³⁺, Tb³⁺, Dy³⁺).
• Characterization of optical properties, including PLQY measurements.
• Femtosecond transient absorption spectroscopy to study defect compensation mechanisms.
• Fabrication and testing of devices for anti-counterfeiting, optical thermometry, and white-light-emitting diodes (WLEDs).

Main Results:

• Achieved an excellent PLQY of 80.1% in RE ion-doped Cs₂NaInCl₆:Sb³⁺ NCs.
• Femtosecond transient absorption revealed that RE ions act as activators and fill deep vacancy defects.
• Demonstrated applications in anti-counterfeiting, optical thermometry with high relative sensitivity (0.753% K^-1 for Sm³⁺ doping), and WLEDs.
• Sm³⁺-doped NCs in a PMMA matrix achieved CIE coordinates (0.30, 0.28), luminous efficiency of 37.5 lm W^-1, CCT of 8035 K, and CRI > 80.

Conclusions:

• RE ion doping significantly enhances the PLQY and optical properties of Sb³⁺-doped Cs₂NaInCl₆ NCs.
• These doped NCs are effective in compensating for vacancy defects, leading to improved performance.
• The developed materials show strong potential as single-component phosphors for next-generation WLEDs and advanced optical sensing applications.