No abstract

Metal nanoparticle plasmons or the photonic crystal effect are being widely used to modify luminescence properties of materials. However, coupling of surface plasmons with photonic crystals are seldom reported for enhancing luminescence of materials. In this paper, a new method for upconversion emission enhancement of rare-earth doped nanoparticles is reported, attributed to the coupling of surface plasmons with photonic band gap effects. Opal/Ag hybrid substrates were prepared by depositing Ag nanoparticles on the top layer of opals by magnetron sputtering. The selective enhancement of red or green upconversion emission of NaYF4:Yb3+,Er3+ nanoparticles on the opal/Ag hybrid substrates is attributed to the coupling effect of surface plasmons and Bragg reflection of the photonic band gap. In addition, the upconversion emission enhancement of NaYF4:Yb3+,Er3+ nanoparticles on the opal/Ag hybrid substrate is attributed to the excitation enhancement was obtained when the excitation light wavelengths overlap with the photonic band gaps of opal/Ag hybrid substrates. We believe that these enhancement effects based on the coupling of metal nanoparticles with the photonic band gap could be extended to other light-emitting materials, which may result in a new generation of lighting devices.

All-inorganic metal halide perovskites of the formulation ABX (where A is Cs, B is commonly Pb, and X is a halide, X = Cl, Br, I) have been studied intensively for their unique properties. Most of the current studies focus on halogen exchange to modify the luminescence band gap. Herein we demonstrate a new avenue for changing the band gap of halide perovskites by designing mixed-monovalent cation perovskite-based colloidal quantum dot materials. We have synthesized monodisperse colloidal quantum dots of all-inorganic rubidium-cesium lead halide perovskites (APbBr, A = mixed monovalent cation systems Rb/Cs) using inexpensive commercial precursors. Through the compositional modulation, the band gap and emission spectra are readily tunable over the visible spectral range of 474-532 nm. The photoluminescence (PL) of RbCsPbBr nanocrystals is characterized with excellent (NTCS color standard) wide color gamut coverage, which is similar to the cesium lead halide perovskites (CsPbX, X = mixed halide systems Cl/Br), and narrow emission line-widths of 27-34 nm. Furthermore, simulated lattice models and band structures are used to explain the band gap variations.

amounts of greenhouse gases, leading to global warming. Widely distributed solar energy is the most abundant and cleanest energy on the earth. Therefore, the conversion of carbon dioxide into renewable hydrocarbons through solar light-driven photocatalysts is an effective strategy to mitigate the environmental crisis. [1,2] Photocatalytic materials have been widely developed since Fujishima's pioneering research work on photocatalytic decomposition of water was reported in 1972. [3] However, single-component semiconductor photocatalysts show low photocatalytic activity due to their rapid charge carrier recombination. Therefore, the development of efficient, inexpensive, and stable photocatalysts has become the key to this technology.In the past few years, perovskite materials have shown excellent photoelectric performance in important research fields such as light-emitting diodes [4,5] and solar cells, [6,7] indicating that perovskite materials have excellent photogenerated charge-carrier generation capabilities. Therefore, they are equally promising for photocatalytic applications. In recent years, halide perovskite nanocrystals have been proved to be capable of photocatalytic CO 2 reduction and the photocatalytic property has been improved by many approaches. [8][9][10] For example, Kong et al. [11] found that in-situ growth of metal-organic framework on the surface of CsPbBr 3 quantum dots can significantly enhance the photocatalytic CO 2 reduction ability. Xu et al. [12] achieved more efficient CO 2 photochemical conversion by composing CsPbBr 3 quantum dots and graphene oxide. However, the poor stability in high humidity or oxygen-rich environment and lead toxicity severely limit their applications. [13,14] Recently, relatively more stable lead-free perovskite materials have likewise shown promising prospects for photocatalytic CO 2 reduction, such as Cs

Cr3+‐doped phosphors have recently gained attention for their application in broadband near‐infrared phosphor‐converted light‐emitting diodes (pc‐LEDs), but generally exhibit low efficiency. In this work, K2Ga2Sn6O16:Cr3+ (KGSO:Cr) phosphor was designed and synthesized. The experimental results show that the Cr3+‐doped phosphor exhibited broadband emissivity in the range 650‐1300 nm, with a full width at half maximum (FWHM) of approximately 220‐230 nm excited by a wavelength of 450 nm. With the co‐doping of Gd3+ ions, the internal quantum efficiency (IQE) of the KGSO:Cr phosphor increased from 34% to 48%. The Gd3+ ions acted neither as activators nor sensitizers, but to justify the crystal field environment for efficient Cr3+ ions broad emission. The Huang‐Rhys factor decreased as the co‐doping of Gd3+ ions increased, demonstrating that the nonradiative transitions were suppressed. An efficient strategy for enhancing the luminescence properties of Cr3+ ions is proposed for the first time. The Gd3+–co‐doped KGSO:Cr phosphor is a promising candidate for broadband NIR pc‐LEDs.