Infrared to Short-Wave Infrared-Emitting Phosphors for Light-Emitting Diode Applications

In the past decade, near-infrared (NIR) materials have been developed for sensor applications. NIR light-emitting diodes (LEDs) facilitate roadside high-accuracy light detection and ranging, thus enhancing driver safety and confidence. With advancements in wearable technology, individuals, particularly young people, have exhibited a desire to track their own health. Thus, nonintrusive light detection is likely to become the mainstream of detection technology. However, short-wave infrared (SWIR) phosphors are still under development. In the present study, we explored materials with the potential for NIR to SWIR emission, such as Eu2+ (ultrahigh crystal field), Cr3+ (six-fold coordination), and Ni2+ (six-fold coordination) activators. Ni2+ is a suitable SWIR activator; however, its blue light (450 nm) absorption ability is weak. The high-efficiency transfer of energy from Eu2+ and Cr3+ to Ni2+ opens a new avenue for research on SWIR phosphors. We further sorted the materials with high potentials for bioimaging and image recognition applications. SWIR light can penetrate deep into biological tissues and be used to observe the characteristic absorption frequencies of various functional groups. Therefore, SWIR light is used in wearable technology, clinical diagnosis, and chair-side dental checkup. With the help of the artificial intelligence of things technology, image recognition facilitates fast and nondestructive detection. In the future, SWIR phosphors, which help avoid high temperature and working noise, may replace traditional halogen lamps. Our findings reveal the key factors influencing SWIR phosphors and provide insights into the application design. The tunable emission of SWIR phosphors in the 1000–1700 nm spectral range facilitates their widespread applications.