Synthesis And Photoluminescence Properties Of Mn⁴⁺-Activated Cs₂MnF₆ And Cs₂NbOF₅ Red Phosphors

White LEDs,known as the fourth-generation solid-state lighting source,have attracted considerable attention from researchers due to its properties of low energy consumption,high energy conversion efficiency,long life and environment friendliness.Based on the InGaN blue chip and YAG:Ce³⁺phosphor powder is the most common combination to achieve white LED,but the lack of red component limits its application in the field of warm white light and backlight display.The Mn⁴⁺activated fluoride red phosphor can be effectively excited by the InGaN blue chip,showing a series of narrow-band red emission at about 630 nm,which is an excellent candidate material for red light emission.In this paper,Cs₂MnF₆ and Cs₂NbOF₅:Mn⁴⁺red phosphors were synthesized by coprecipitation method.The luminescence characteristics of Mn⁴⁺in Cs₂MnF₆ and Cs₂NbOF₅:Mn⁴⁺phosphors and their potential applications in LED devices were discussed.The main research contents of this paper are as follows:?1?Red emission phosphors Cs₂MnF₆,Cs₂MnF₆:Sc³⁺and Cs₂MnF₆:Si⁴⁺were synthesized successfully by a co-precipitation method.The Rietveld refinement of X-ray diffraction reveals that this red phosphor exhibits a cubic structure in Fm3?m space group.Owing to the Mn⁴⁺as a part of matrix,this kind of red phosphor possesses an extremely high AE,which can be promoted to 88%.The doping of Sc³⁺and Si⁴⁺ions into Cs₂MnF₆ can effectively increase the luminescence intensity to 253%and 232%,respectively,relative to Cs₂MnF₆.The relative emission intensity of Cs₂MnF₆:5%Si⁴⁺red phosphor preserves about 115%when temperature rises to 175?.By employing Cs₂MnF₆:5%Si⁴⁺as a red emitting component,high-performance LED-1 with Ra=86.2,R9=82.1 and CCT=3297 K,and LED-2 with an ultra-wide color gamut?NTSC value of 122.3%and Rec.2020 value of 91.3%?are obtained.?2?A novel non-rare-earth and nonequivalent doping type of Cs₂NbOF₅:Mn⁴⁺oxyfluoride red-emitting phosphor with high luminous efficiency was obtained via a facile room-temperature co-precipitation method and its morphology,and luminescent properties were investigated in detail.The Cs₂NbOF₅:Mn⁴⁺phosphor with micro-rod-like morphology has broad band absorption at blue light region?⁴74 nm?and narrow bandwidth emissions at red region?⁶33 nm?.The color purity of Cs₂NbOF₅:Mn⁴⁺phosphor is calculated to be about 99%and the internal quantum yield under 474 nm excitation is 63.4%.The concentration quenching of Mn⁴⁺in Cs₂NbOF₅ matrix is mainly due to the dipole-dipole interaction and the activation energy of temperature-quenching is calculated to be⁰.2610 eV.The demonstration of a blue InGaN LED chip in combination with a blend of newly developed Cs₂NbOF₅:Mn⁴⁺red phosphor and YAG:Ce³⁺yellow phosphor greatly decreased the correlated color temperature?CCT?from 6255 to 3517 K,while significantly improving the color rendering index?CRI?from 72.5 to 87.5.