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Combining rare-earth ions (RE3+) in halide perovskites is a hopeful strategy to produce interesting optical properties in visible and near-infrared (NIR) regions. Here, RE3+(RE: Nd, Ho, Er, Tm) ions are successfully introduced into Cs4Cd1–wMnwBi2Cl12(0 ≤ w≤ 1) vacancy-ordered quadruple perovskites through a facile hydrothermal method. In addition to the strong orange-red Mn2+emission, the as-prepared materials exhibit the effective characteristic emission of RE3+in the red and NIR regions viaconstructing a Mn2+energy bridge. With Mn2+gradually replacing Cd2+in Cs4Cd1–wMnwBi2Cl12:RE3+, the photoluminescence (PL) of RE3+in the red and NIR ranges shows an increasing trend until it reaches the strongest value (w= 1). The energy transfer processes of [BiCl6]3–→ Mn2+→ RE3+are confirmed, and the corresponding mechanism is explored. According to the manipulation of the Mn2+/Cd2+component, an evolution process from direct to indirect band gaps is verified viaa combined experimental–theoretical approach. White light-emitting diodes (LEDs) are fabricated by employing Ho3+-doped Cs4MnBi2Cl12on near-ultraviolet (n-UV) LED chips, achieving an improved color rendering index (CRI) from 83.3 to 93.0 compared to that of the parent compound. Codoping RE3+(RE: Nd, Ho, Er, Tm) ions into Cs4MnBi2Cl12results in an ultrawide emission covering both NIR I and NIR II regions, implying a great potential for NIR detection application.

The development of narrow-band emitting phosphors is still a pivotal challenge for light-emitting diode (LED) backlights in liquid-crystal displays (LCDs). Hereon, an effective tactic is raised to develop a novel narrow-band violet emission in Eu2+-doped BaLiZn3(PO4)3with a highly symmetric site and rigid crystal structure. Under the ultraviolet (UV) light excitation of 334 nm, this novel BLZPO:Eu2+shows a super narrow-band violet emission at 387 nm with a full width at half-maximum (fwhm) of 11 nm at 7 K and 18 nm at 298 K, respectively. Such an ultranarrow-band emission has never been achieved in the previous Eu2+-doped phosphors. Moreover, this as-prepared BLZPO:Eu2+phosphor presents small photoluminescence (PL) thermal quenching, and its PL intensity maintains 82.6% at 150 °C and 70% at 200 °C of the initial PL intensity at room temperature. The as-fabricated LED utilizing BLZPO:Eu2+with the n-UV LED exhibits potential anticounterfeiting application. This study offers a novel idea to achieve the supernarrow-band emission of Eu2+-activated phosphors based on the highly symmetric crystal structure.

In the pursuit of high efficiency and wide color gamut in displays, there is still an urgent demand for high-performing narrow-band green-emitting phosphors. Inspired by a mineral UCr4C4-type structure with a highly condensed framework, a novel narrow-band green-emitting Na3K5(Li3SiO4)8:Eu2+(NKLSO:Eu2+) phosphor is designed. This phosphor exhibits a green emission peaking at 525 nm with a full width at half-maximum (fwhm) of 43 nm. The narrow-band emission is associated with the highly symmetric sites for Eu2+. Benefiting from its high structural rigidity, this NKLSO:Eu2+phosphor shows a very low photoluminescence (PL) thermal quenching, maintaining 96%@150 °C integrated PL intensity of the original PL intensity. Moreover, by incorporating a small amount of Al3+into the lattice, the internal quantum efficiency (QE) and external QE of this phosphor is enhanced from 70 to ∼100% and 21 to 38%, respectively. The as-fabricated wLED-1 (InGaN chip@blue, NKLSO:1.25% Eu2+@green, KSiF6:Mn4+@red) shows a wide color gamut (106% NTSC), demonstrating vivid photographs when used in a projector. The as-fabricated wLED-4 (BaMgAl10O17:Eu2+@blue, NKLSO:1.25% Eu2+@green, CaAlSiN3:Eu2+@red) presents a low correlated color temperature of 5390 K and a high color rendering index (Ra) of 86.9. These results show that narrow-band green-emitting NKLSO:Eu2+has potential applications in both backlight displays and solid-state lighting.