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The last decades have witnessed the discovery of tens of thousands of rare earth (RE) (e.g., Eu2+) and non-RE (e.g., Mn2+) doped photonic materials for near-ultraviolet (NUV) and blue converted white light-emitting diodes (wLEDs), but the future development of wLEDs technology is limited greatly by the intrinsic problems of these traditional dopants, such as the insurmountable visible light reabsorption, the weak absorption strength in NUV or blue region, and so on. Here we report a feasible strategy guided by density functional theory (DFT) calculation to discover novel Bi3+ red luminescent materials, which can solve the above problems eventually. Once the untraditional ion of bismuth is doped into ZnWO4 crystal, multiple defects can be possibly created in different charge states such as BiZn, BiW, interstitial Bi, and even defect complexes of 2 BiZnVW among others, and they, as DFT calculated results illustrate, have the potential to produce emission spanning from visible to near-infrared. As confirmed by experiment, tunable emission can be led to cover from 400 to 800 nm after controls over temperatures, defect site-selective excitation schemes, and the energy transfer between these defects and host. A novel red luminescence was observed peaking at ∼665 nm with a broad excitation in the range of 380–420 nm and no visible absorption, which is evidenced by the temperature-dependent excitation spectra and the diffuse reflection spectra. DFT calculation on defect formation energy shows that BiZn 3+, the valence state of which is identified by X-ray photoelectron spectroscopy, is the most preferentially formed and stable defect inside a single Bi-doped ZnWO4 crystal, and it produces the anomalous red luminescence as confirmed by the single-particle level calculations. Calculation based on dielectric chemical bond theory reveals that the high covalency of the lattice site which Bi3+ prefers to occupy in ZnWO4 is the reason why the emission appears at longer wavelength than the previously reported compounds. On the basis of this work, we believe that future combination of DFT calculation and dielectric chemical bond theory calculation can guide us to efficiently find new phosphors where Bi3+ can survive and emit red light upon NUV excitation. In addition, the DFT calculation on Bi defects in different charge states will help better understand the longstanding as yet unsolved problem on the mechanism of NIR luminescence in bismuth-doped laser materials.

Bi-activated photonic materials have received increased interest recently because they can be excited effectively with near-ultraviolet (NUV) but not visible light, thereby avoiding the reabsorption among phosphors, which cannot be solved intrinsically by traditional rare earth (e.g., Eu, Ce) phosphors. Such unique property suggests their potential application in NUV chip-based WLEDs. However, few Bi phosphors exhibit strong excitation peak in NUV, though the excitation tail of some can extend to NUV. Herein, we report a novel yellow-emitting LaBWO:Bi (LBW:Bi) phosphor with strong NUV excitation. The photoluminescence (PL) spectroscopy analysis indicates that there are two Bi luminescent centers in LBW:Bi phosphor, which is clearly in contradiction with the established hexagonal structure of LaBWO with P6 space group because only one La site in this structure can accommodate Bi ions. Combining the luminescent properties of Bi with Rietveld refinement, LaBWO was redefined as a trigonal structure with the lower space group of P3 in which there are two independent crystallographic La sites. In addition, the rationalization of P3 space group was further confirmed by the finding of the reflection (0001) according to the extinction rule. Therefore, the PL behavior of Bi can act as a complementary tool to determinate the real crystal structure especially when it is hard to distinguish by conventional X-ray diffraction techniques.

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.

Here, a cheap and fast way to measure the CO 2 absorption rate and capacity through thermogravimetric analysis (TGA) is proposed. The absorption of CO 2 in 11 ILs varying in anion, cation, alkyl chain length, and C2 methylation was then investigated. Three parameters comprehensively characterizing the absorption capacity and kinetics, including the absorption capacity (x), the initial absorption rate (r 10 ), and the degree of difficulty to reach phase equilibrium (t 0.9 ), were proposed as the standards to evaluate the potential of ILs for CO 2 capture. Results show that the correlation between absorption capacity and the degree of difficulty to reach phase equilibrium is complicated. However, ILs with higher absorption capacity usually have a higher initial absorption rate, suggesting a simple way to estimate absorption capacity just by determining initial absorption rate for less than 10 min. More importantly, ILs with the acetate ([Ac]) anions have an advantage in x, r 10 , and t 0.9 over other ILs, indicating that [Ac]-based ILs are promising candidates for CO 2 capture in practice.