Design of Novel Highly Efficient Yellow-Orange Color-Tunable Luminescence in Rb₂Sr_1–yCa_yP₂O₇:xEu²⁺ Solid Solutions for White Light-Emitting Diodes

Abstract

Traditional white light-emitting diodes (WLEDs) are limited by the energy loss due to reabsorption. Integrating binary complementary color phosphors with near-ultraviolet (n-UV) LED chips can be a good solution, and the core of it is to develop yellow-emitting phosphors. In this work, we have designed Rb 2 Sr 1−y Ca y P 2 O 7 :xEu 2+ solid solutions with yelloworange color-tunable luminescence. The crystal structure, luminescence properties, and potential applications for WLEDs were explored systematically. Under n-UV light excitation, the phosphors efficiently emit broadband yellow-orange emission. The reasons and mechanisms of the variation of the PL/PLE spectra have been investigated. The optimal Rb 2 SrP 2 O 7 :0.5% Eu 2+ sample exhibits a high quantum efficiency of 72.96% with a good color purity of 87.1%. Upon combination of the BAM:Eu 2+ and Rb 2 SrP 2 O 7 :0.5% Eu 2+ phosphors with a 380 nm n-UV chip, a WLED device is fabricated and can emit white light with good performance.

Investigation of the Solid-Solution Limit, Crystal Structure, and Thermal Quenching Mitigation of Sr-Substituted Rb2CaP2O7:Eu2+ Phosphors for White LED Applications

“…14). It is worth noting that as reported earlier by Zhang et al 22 refinement was conducted using the structure of Rb 2 SrP 2 O 7 (space group C2/c, no. 15) as a model.…”

“…In the case of Rb 2 CaP 2 O 7 :Eu 2+ , Hong et al reported that at 140 °C this reddish-orange-emitting phosphor retained only ∼30% of the initial integrated intensity (∼30%@140 °C). 19 22 Nevertheless, the thermal quenching issue has not been studied in their work and is unknown. Thus, boosting the luminescence thermal stability of phosphors is vital to enabling their potential applications.…”

“…Pyrophosphate phosphors with such a thermal quenching issue are practically not suitable in pc-WLED applications. Recently, Zhang et al reported the preparation and room-temperature PL properties of Rb 2 Sr 1– y Ca y P 2 O 7 : x Eu 2+ solid-solution phosphors . Nevertheless, the thermal quenching issue has not been studied in their work and is unknown.…”

Tailoring the Luminescent Properties of SrS:Ce3+ by Sr-Deficiency and Na+ Doping

“…Phosphor-converted white light-emitting diode (pc-wLED) lighting has acquired incredible accomplishment since the successful invention of the InGaN blue LED by Isamu Akasaki et al, awarded the Nobel Physics Prize in 2014 . Presently, pc-wLEDs have become an increasingly hot topic due to a wealth of unique advantages, such as environmental friendliness, long lifetime, and tunable colors allowing for a wide utilization in the fields of bioimaging, anticounterfeiting, lighting, medical applications, and many more. − Exploring classical phosphors, being the essential ingredient of solid-state lighting emitting diodes (SS-LEDs), has been performed by introducing rare earth (RE) ions into inorganic host materials. − In the early 1990s, the phosphors of alkali-earth metal sulfides (MgS, CaS, SrS, and BaS) doped with Eu 2+ , Eu 3+ , and Ce 3+ were extensively studied for cathodoluminescence and electroluminescence displays. , A series of commercial CaS:Eu phosphors have recently been investigated as solid-state light sources due to the red emission near 645 nm. SrS is considered as a potential substrate matrix owing to its small vibrational frequencies and narrow band gap energy. , The luminescence properties of SrS can be modulated over the entire region of the visible electro-magnetic spectrum when doped with appropriate RE ions.…”

Effects of activated Sr 2+ ion content on strong blue‐emitting Ca 2 Sb 2 O 7 materials for high‐quality WLED devices

“…The pc‐WLEDs have outstanding characteristics of energy saving, 5 fast response, 6 high luminous efficiency, 7 stable output, 8 long service time, 9 etc with respect to conventional incandescent lamps. Generally, the previous fabrication technique involving the pc‐WLEDs based on only yellow‐emitting phosphors (Y 3 Al 5 O 12 :Ce 3+ ) onto a blue LED chip would suffer from low color rendering index (CRI) (<75) 10,11 and high correlated color temperature (CCT) (>7000 K) 12 which are not suitable for indoor lighting due to the blue light affects 13 . Fortunately, the combination of blue/green/red‐emitting phosphors covered on the near‐ultraviolet (NUV) and ultraviolet (UV) LED chips is well‐known as a popular approach to fabricate the pc‐WLEDs by avoiding the above disadvantages.…”