Broad-Band Near-Infrared Emission with High External Quantum Efficiency from Molybdenum-Doped Vacancy-Ordered Double Perovskites for Spectroscopic Analysis

Broad-band
near-infrared (NIR) luminescent materials are crucially
important components of NIR light-emitting devices (LEDs) and have
garnered significant attention for their wide-ranging applications
in spectroscopy analysis. Here, we present vacancy-ordered double
perovskite Cs2HfCl6 single crystals, which achieve
efficient broad-band NIR emission through Mo4+ ion doping.
The optimized sample has an internal quantum efficiency of 85.1% and
an ultrahigh external quantum efficiency of 68.3%. Experimental characterizations
and theoretical calculations reveal that intense NIR emission arises
from dopant-induced d–d transitions. In addition, the as-synthesized
NIR-emitting perovskites retain 58% of the photoluminescence intensity
at 425 K compared to 300 K. The NIR LED light source fabricated by
the NIR-emitting samples exhibits promising potential for application
in NIR spectroscopy analysis, night vision, and nondestructive testing.
This work provides insights into the electronic transitions in Mo4+-activated broad-band NIR-emitting perovskites and opens
up a new horizon for designing high-performance broad-band NIR luminescence.