Novel red-emitting phosphors A₂HfF₆:Mn⁴⁺(A = Rb⁺, Cs⁺) for solid-state lighting

Abstract

New red-emitting phosphors AHfF:Mn (A = Rb, Cs) with a single phase have been successfully synthesized via a simple ion exchange method, and their structures and luminescence properties were investigated. It was found that Mn ions in RbHfF and CsHfF who share wide band gaps can possess broad excitation bands in the blue regions and intense red emission with internal quantum yields of 0.556 and 0.652, respectively. Meanwhile, these red phosphors exhibit high chemical and thermal stabilities. A series of LED devices with a tunable color rendering index and color temperature were fabricated with these samples which can remarkably optimize the optical performances of white light-emitting diodes (w-LEDs). These results indicate that AHfF:Mn phosphors can be promising red phosphors in w-LEDs.

First‐principles and crystal‐field calculations of the electronic and optical properties of two novel red phosphors Rb2HfF6:Mn4+ and Cs2HfF6:Mn4+

“…As a next step, the crystal field Hamiltonian with the CFPs from Table was diagonalized in the space spanned by all wave functions of the Mn 4+ LS terms (8 LS terms in total, 120 states). The lowest calculated energy levels located in the spectral range studied experimentally are collected in Table and exhibited in Figure along with the experimental optical spectra of the studied materials . Agreement between the calculated and experimental data is good, including the positions of the calculated levels, widths of the orbital triplet splittings.…”

“…Experimental spectra (adopted from Ref. , solid lines) and calculated Mn 4+ energy levels (this work, vertical lines) of Rb 2 HfF 6 :Mn 4+ (A) and Cs 2 HfF 6 :Mn 4+ (B) [Color figure can be viewed at wileyonlinelibrary.com]…”

“…An important question in the analysis of the Mn 4+ emission spectra is the ZPL location. Detailed analysis of the experimental data allowed us to set the ZPL of the 2 E 2 – 4 A 2 emission transition at 622 nm, or 16 077 cm −1 . This agrees with the ZPL energy position found in Ref.…”

“…Research aimed at developing new Mn 4+ ‐based phosphors for LED devices is receiving considerable attention due to the commercialization of the K 2 SiF 6 :Mn 4+ phosphor. Recently, 2 novel red‐emitting phosphors A 2 HfF 6 :Mn 4+ ( A =Rb, Cs) with emission in the required 590–650 nm wavelength range have been reported. Details of the synthesis, optical properties including first‐principles calculations pertaining to the band structure of the Rb 2 HfF 6 host were described .…”

“…Recently, 2 novel red‐emitting phosphors A 2 HfF 6 :Mn 4+ ( A =Rb, Cs) with emission in the required 590–650 nm wavelength range have been reported. Details of the synthesis, optical properties including first‐principles calculations pertaining to the band structure of the Rb 2 HfF 6 host were described . The goal of our study is to considerably extend the initial studies by including the crystal‐field calculations of the Mn 4+ energy levels in both hosts and by performing first‐principles analysis of the structural, electronic, and optical properties of Rb 2 HfF 6 , Cs 2 HfF 6 and the mixed RbCsHfF 6 phosphors.…”