1 research outputs found
Highly Efficient and Thermally Stable K<sub>3</sub>AlF<sub>6</sub>:Mn<sup>4+</sup> as a Red Phosphor for Ultra-High-Performance Warm White Light-Emitting Diodes
Following pioneering
work, solution-processable Mn<sup>4+</sup>-activated fluoride pigments,
such as A<sub>2</sub>BF<sub>6</sub> (A = Na, K, Rb, Cs; A<sub>2</sub> = 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 K<sub>3</sub>AlF<sub>6</sub>:Mn<sup>4+</sup> 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 Mn<sup>4+</sup> ions at the distorted octahedral sites in K<sub>3</sub>AlF<sub>6</sub>:Mn<sup>4+</sup> 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 K<sub>3</sub>AlF<sub>6</sub> may be a highly suitable candidate for fabricating high-performance
warm W-LEDs