Selecting nitride host for Yb3+ toward near-infrared emission with low-energy charge transfer band

Yb³⁺-doped phosphors have characteristic near-infrared (NIR) emissions, but their applications in phosphor-converted light-emitting-diodes (pc-LEDs) and Si solar cells are limited due to their mismatching excitation spectra. Here, we selected nitride La₃Si₆N₁₁ (LSN) as host material to achieve Yb³⁺ NIR emission upon low-energy charge transfer (CT) excitation. The obtained phosphor LSN:Yb³⁺ has a broad CT excitation band ranging from 250 to 500 nm and narrowband NIR emissions ranging from 950 to 1100 nm centered at 983 nm. On the basis of spectral data, the vacuum referred binding energies (VRBE) schemes are constructed to locate energy levels of all lanthanide ions in LSN. We also fabricated NIR pc-LED device using 395 nm LED chip to demonstrate the potential applications of LSN:Yb³⁺ phosphors.