Blue light‐excitable Eu‐doped yellow emitting borate KSr₄B₃O₉ phosphor for white light‐emitting diodes

Abstract

In the development of novel phosphors for solid-state light applications, the suitable excitation peak matching with blue LED chip was usually neglected. However, the excitation peak of phosphors was strongly related to the Stocks shift, crystal field splitting, and centroid shift. Here, an environmentally friendly borate phosphor KSr 4 B 3 O 9 : Eu 2+ with the maximum excitation peak position at ∼460 nm was prepared in a quite mild synthesis condition. With a blue light excitation, KSr 4 B 3 O 9 : Eu 2+ phosphors could emit a bright yellow light centered at ∼560 nm, which could be attributed to the drastic centroid shift and strong crystal field splitting. The strong electron cloud overlaps between Eu-O and the high electron density on the O atom turned out to be the main reason that induces the strong nephelauxetic effect. In addition, the strong crystal field splitting was benefited to the relatively short average Sr-O distance and the large Sr-O distances distribution range from ∼2.23 to 2.96 Å. Meanwhile, the Eu 2+ occupation of all the Sr 2+ sites in KSr 4 B 3 O 9 host identified by Rietveld refinement, cryogenic emission spectra, and Eu 3+ fluorescent probe gave another evidence to the wide absorption region. The final WLED device and three-dimensional colorful artwork were fabricated and displayed to suggest a potential application in the solid-state lighting field and some expressions of esthetic concepts.

Photoluminescence properties of europium-activated double layered perovskite Sr3Ti2O7 for high-quality lighting applications

“…Moreover, the excitation spectra displayed several sharp peaks in the higher wavelength region, attributed to the characteristic f–f transitions of Eu 3+ ions. 27 These peaks originated from transitions between the ground state 7 F 0 and various excited states of the Eu 3+ ion upon absorption of UV light. These transitions were centered at 382 nm ( 7 F 0 → 5 L 7 ), 395 nm ( 7 F 0 → 5 L 6 ), 415 nm ( 7 F 0 → 5 D 3 ), and 464 nm ( 7 F 0 → 5 D 2 ).…”

Highly efficient blue‐emitting phosphor via charge compensation strategy and its application for white LED lighting

“…But this approach exhibits a strong blue spike derived from unconverted blue light in the InGaN chip 6–8 . The blue spike disrupts the normal biological rhythm of the human body resulting in sickness, like circadian disruption and mood disorders 9–12 . These problems can be solved by using the near‐ultraviolet (n‐UV) light pumped WLEDs consisting of red, green, and blue phosphors 13–16 .…”

“…These problems can be solved by using the near‐ultraviolet (n‐UV) light pumped WLEDs consisting of red, green, and blue phosphors 13–16 . In this scheme, high‐efficiency phosphors with appropriate excitation and emission spectra are obviously the key components for high‐quality WLEDs 12,17–20 …”

“…[6][7][8] The blue spike disrupts the normal biological rhythm of the human body resulting in sickness, like circadian disruption and mood disorders. [9][10][11][12] These problems can be solved by using the near-ultraviolet (n-UV) light pumped WLEDs consisting of red, green, and blue phosphors. [13][14][15][16] In this scheme, high-efficiency phosphors with appropriate excitation and emission spectra are obviously the key components for high-quality WLEDs.…”

“…[13][14][15][16] In this scheme, high-efficiency phosphors with appropriate excitation and emission spectra are obviously the key components for high-quality WLEDs. 12,[17][18][19][20] The activators and host materials are crucial for conceiving appropriate phosphor. [21][22][23][24] Among the lanthanides, Ce is often used as activators for obtaining broader emission band phosphors because of the parity allowed 4f−5d electric dipole transition.…”