title: Highly Efficient and Thermally Stable K3AlF6:Mn4+as a Red Phosphor for Ultra-High-Performance Warm White Light-Emitting Diodes.
abstract: Following pioneering work, solution-processable Mn4+-activated fluoride pigments, such as A2BF6(A = Na, K, Rb, Cs; A2= Ba, Zn; B = Si, Ge, Ti, Zr, Sn), have attracted considerable attention as highly promising red phosphors for warm white light-emitting diodes (W-LEDs). To date, these fluoride pigments have been synthesized via traditional chemical routes with HF solution. However, in addition to the possible dangers of hypertoxic HF, the uncontrolled precipitation of fluorides and the extensive processing steps produce large morphological variations, resulting in a wide variation in the LED performance of the resulting devices, which hampers their prospects for practical applications. Here, we demonstrate a prototype W-LED with K3AlF6:Mn4+as the red light component via an efficient and water-processable cation-exchange green route. The prototype already shows an efficient luminous efficacy (LE) beyond 190 lm/W, along with an excellent color rendering index (Ra = 84) and a lower correlated color temperature (CCT = 3665 K). We find that the Mn4+ions at the distorted octahedral sites in K3AlF6:Mn4+can produce a high photoluminescence thermal and color stability, and higher quantum efficiency (QE) (internal QE (IQE) of 88% and external QE (EQE) of 50.6%.) that are in turn responsible for the realization of a high LE by the warm W-LEDs. Our findings indicate that the water-processed K3AlF6may be a highly suitable candidate for fabricating high-performance warm W-LEDs.
authors.affiliation: State Key Laboratory of Luminescent Materials and Devices and Institute of Optical Communication Materials, South China University of Technology , Guangzhou 510641, China.
authors.forename: Enhai
authors.initials: E
authors.lastname: Song
authors.affiliation: Guangzhou LEDteen Optoelectronics Co., Ltd. Guangzhou 510663, China.
authors.forename: Jianqing
authors.initials: J
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Luminescent Materials and Devices and Institute of Optical Communication Materials, South China University of Technology , Guangzhou 510641, China.
authors.forename: Jiahao
authors.initials: J
authors.lastname: Shi
authors.affiliation: State Key Laboratory of Luminescent Materials and Devices and Institute of Optical Communication Materials, South China University of Technology , Guangzhou 510641, China.
authors.forename: Tingting
authors.initials: T
authors.lastname: Deng
authors.affiliation: State Key Laboratory of Luminescent Materials and Devices and Institute of Optical Communication Materials, South China University of Technology , Guangzhou 510641, China.
authors.forename: Shi
authors.identifier: http://orcid.org/0000-0001-9625-8222
authors.initials: S
authors.lastname: Ye
authors.affiliation: State Key Laboratory of Luminescent Materials and Devices and Institute of Optical Communication Materials, South China University of Technology , Guangzhou 510641, China.
authors.forename: Mingying
authors.initials: M
authors.lastname: Peng
authors.affiliation: State Key Laboratory of Optoelectronic Materials and Technologies, School of Chemistry and Chemical Engineering, Sun Yat-Sen University , Guangzhou 510275, P.R. China.
authors.forename: Jing
authors.identifier: http://orcid.org/0000-0002-1246-991X
authors.initials: J
authors.lastname: Wang
authors.forename: Lothar
authors.initials: L
authors.lastname: Wondraczek
authors.affiliation: State Key Laboratory of Luminescent Materials and Devices and Institute of Optical Communication Materials, South China University of Technology , Guangzhou 510641, China.
authors.forename: Qinyuan
authors.identifier: http://orcid.org/0000-0001-6544-4735
authors.initials: Q
authors.lastname: Zhang
keywords: green route; luminous efficiency; red phosphor; ultrahigh performance; warm white LEDs