NIR-II-to-NIR-II upconversion and covert optical encryption in lanthanide halide double perovskites

Area of Science:

• Materials Science
• Photonics
• Nanotechnology

Background:

• Near-infrared-II (NIR-II) to NIR-II upconversion is crucial for advanced photonics but is hindered by concentration quenching in sensitizers like Erbium (Er3+).
• Developing materials that efficiently manage high sensitizer concentrations is essential for overcoming these limitations.

Purpose of the Study:

• To engineer a lanthanide halide double perovskite for efficient NIR-II to NIR-II upconversion.
• To overcome the challenge of concentration quenching in highly concentrated Er3+ sensitizers.
• To explore multicolor tunability and optical encoding applications.

Main Methods:

• Synthesis of a lanthanide halide double perovskite material.
• Utilizing a dense Er3+ excitation network for energy harvesting and migration.
• Incorporating Thulium (Tm3+), Neodymium (Nd3+), Holmium (Ho3+), and Ytterbium (Yb3+) ions.
• Investigating energy transfer mechanisms including Er3+→Tm3+ transfer and Er-Yb cross-relaxation.

Main Results:

• Achieved efficient NIR-II to NIR-II upconversion under 1550 nm excitation.
• Demonstrated strong NIR-II Tm3+ emission via efficient Er3+→Tm3+ energy transfer.
• Enhanced 1220 nm emission through Yb3+ as an intermediate energy bridge.
• Exhibited excitation-dependent multicolor tunability via Er-Yb cross-relaxation.
• Showcased multilevel optical encoding for anticounterfeiting and encryption.

Conclusions:

• The developed lanthanide halide double perovskite effectively addresses concentration quenching in Er3+ sensitizers for efficient upconversion.
• The material demonstrates potential for advanced optical encoding, anticounterfeiting, and wavelength-selective encryption applications.