“…Fluorides have relatively low phonon energy and weak electron–phonon coupling (EPC) effect on the d–d transition of Cr 3+ compared with oxides, which will be beneficial for developing the Cr 3+ NIR luminescence performances. , Song et al reported a Cr 3+ -doped fluoride of K 2 NaScF 6 :Cr 3+ with excellent luminescence thermal stability (89.6%), a high internal quantum efficiency (IQE = 74%), and an FWHM of 101 nm, which demonstrates that Cr 3+ -doped fluoride has great potential for NIR pc-LEDs application . Besides, Na 3 AlF 6 (λ max = 720 nm, IQE = 75%, FWHM = 95 nm), K 3 AlF 6 :Cr 3+ , and K 3 GaF 6 :Cr 3+ (λ max = 783 nm, IQE = 25 and 28%, FWHM = ∼100 nm) were also reported for NIR pc-LED application.…”