Shala Bi

Bio: Shala Bi is an academic researcher from Pukyong National University. The author has contributed to research in topics: Luminescence & Phosphor. The author has an hindex of 7, co-authored 13 publications receiving 206 citations.

Optical Thermometry Based on Vibration Sidebands in Y2MgTiO6:Mn4+ Double Perovskite

Abstract: Mn4+-doped Y2MgTiO6 phosphors are synthesized by the traditional solid-state method. Powder X-ray diffraction, scanning electron microscope, and energy-dispersive X-ray spectrometer are employed to...

On the absorption spectra of complex ions. II

Abstract: The secular determinants obtained in the previous paper are solved for the energy levels which are important in the absorption spectra of the normal complex ions, leaving the crystalline field strength as a parameter. The values of B and C (Racah's parameters) there needed are determined from the observed spectra of free ions or in some cases by extrapolation. The f -values of the transitions which connect the energy levels calculated are estimated and compared with the observed intensities. The difference of the spectral width among absorption bands and lines is also considered using the energy diagram obtained. Following the assignments determined by the above considerations, the calculated positions of lines and bands are rather in good agreement with the experimental data in divalent ions [MX 6 ] 2+ (M=Cr, Mn, Fe, Co, Ni), when we adjust the crystalline field parameter D q suitably. In trivalent ions [MX 6 ] 3+ (M=Ti, V, Cr, Mn, Fe), it is necessary besides the adjustment of D q to use smaller values ...

Luminescent perovskites: recent advances in theory and experiments

Abstract: Perovskites form an important and enormous class of inorganic compounds. Recently, perovskite materials have attracted extensive research interest owing to their excellent optoelectronic properties. Deep insights into the relationships between the crystal structure, electronic structure and properties play an important role in the development of new functional materials and high-performance devices. In this review, after a brief introduction, we first discuss the crystal structure and crystal chemistry of perovskites according to their three classes: standard perovskites, low-dimensional perovskites and perovskite-like halides. Next, the electronic structure and luminescence from different physical origins are presented. Then, we present a survey on the design, synthesis and luminescence properties of different perovskites, including halide perovskites, oxide perovskites, and lanthanide- or transition metal-doped perovskites, also including dimension-different perovskites (3D, 2D, 1D and quantum dots). We also summarize the strategies for improving the photoluminescence quantum yield (PLQY) and chemical stability, including by surface passivation, encapsulation and doping. Finally, we review their applications and give a brief outlook.

Bismuth-based photocatalysts for solar energy conversion

Abstract: Semiconductor photocatalysis is a promising technology for solar fuel production and environmental remediation. However, the solar energy conversion efficiency is far from satisfactory, which restricts its practical application. The development of semiconductor materials is crucial to promote the solar energy conversion efficiency in photocatalytic systems. Owing to the Bi 6s and O 2p hybrid orbitals in the valence band, most of the bismuth-based photocatalysts possess a narrow bandgap for visible light utilization, which has attracted increasing attention. In the past few years, a rich family of bismuth-based photocatalysts have been developed, which are yet to be comprehensively reviewed. In this review article, the recent progress of bismuth-based nanomaterials for photocatalysis including pollutant degradation, water splitting, CO2 reduction, N2 fixation, and organic synthesis is critically reviewed. In particular, promising strategies for promoting the photocatalytic activity of each material system is discussed and the key challenges and prospects of bismuth-based materials for photocatalysis are presented, which are believed to promote the development of this important research field.

A broadband cyan-emitting Ca 2 LuZr 2 (AlO 4 ) 3 :Ce 3+ garnet phosphor for near-ultraviolet-pumped warm-white light-emitting diodes with an improved color rendering index

Abstract: Finding efficient cyan phosphors with broadband absorption in the near-ultraviolet range (380–420 nm) and bright emission around 490 nm are highly important to make up for the so-called cyan gap (480–520 nm) in traditional tricolor (blue, green and red) phosphor-converted white light-emitting diodes (LEDs). Herein, we reported a new garnet phosphor, namely Ca2LuZr2(AlO4)3:Ce3+ (CLZA:Ce3+), with a cyan-emitting band, which enabled to fill the cyan gap and realize high color rendering white LEDs. The composition-optimized CLZA:1% Ce3+ phosphors showed an intense broad excitation band in the 370–475 nm wavelength range peaked at 408 nm and a broad asymmetric emission band at around 483 nm in the wavelength range of 414–650 nm. Importantly, the cyan-emitting CLZA:1% Ce3+ phosphors possessed a luminescence efficiency of 58%. Notably, the CLZA:1% Ce3+ cyan phosphors allowed to fill the cyan gap between the blue and green emission bands in white LEDs, and the value of color rendering index could be enhanced from 82.3 to 89.2. This study provides new insights into designing and developing suitable efficient phosphors for high-color-quality solid-state white lighting.

Review—Mn4+-Activated Red and Deep Red-Emitting Phosphors

Abstract: Mn4+-activated phosphors are a new class of non-rare earth phosphors and are alternative to commercial Eu2+-activated nitride/oxynitride phosphors with growing interest in various applications. In this review article, the structural and photoluminescence (PL) properties of various Mn4+-activated phosphors have been discussed. The host materials considered here can be roughly classified into five groups; fluorides, oxides, oxyfluorides, and two fluorine compounds. Phosphors of each group can also be classified into totally eleven subgroups from their different PL spectral features, e.g., whether an appearance of the zero-phonon line (ZPL) emission peak or not. The ZPL emission and absorption energies of the Mn4+ ions have been determined from the PL and PL excitation spectra using the Franck−Condon analysis method within the configurational-coordinate (CC) model. These results are used to obtain reliable phosphor parameters, i.e., the crystal-field (Dq) and Racah parameters (B and C), of the Mn4+ ions in the various host materials. The PL intensity vs temperature data, together with those of the luminescence lifetimes, are modeled on the basis of the CC model, and an excellent agreement has been achieved if not only the optical phonon but also the acoustic phonon contribution is taken into consideration in the conventional thermal quenching model. Effects of the hydrostatic pressure and dopant concentration on the PL spectral features are also discussed. Finally, key properties of the Mn4+-activated phosphors are discussed for use of such red and deep red-emitting phosphor systems in warm w-LED and indoor plant cultivation applications. © The Author(s) 2019. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 License (CC BY, http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse of the work in any medium, provided the original work is properly cited. [DOI: 10.1149/2.0022001JSS]