Critical Review—A Promising Cs₃CoCl₅ Prototype Phosphor toward the Discovery of Next-Generation LED Phosphor

Abstract

To improve and identify next-generation solid-state lighting devices, there is an urgent need to discover new and highly efficient phosphor materials. Currently, the preparation of phosphor materials is considered to be an art rather than science and is based on finding crystal structures that can act as hosts for the activator ions. Thus far, there has been no systematic analysis on how to select host structures for given activator ions such that the synthesized phosphor is efficient. In this review, the general strategies for tuning and enhancing the photoluminescence properties of phosphor materials for white light-emitting diodes are discussed with respect to versatile host materials belonging to the Cs3CoCl5 family. Furthermore, we also discuss several important parameters for constructing the sort diagram for selecting efficient host materials.

To Luminesce or to Change Valence? Insight into the Wavelength Dependency of the Reversible Valence Switching of Europium in Sr3SiO5

“…Figure 1a provides the XRD patterns of Sr ] tetrahedra along the c-axis. 42 The representative morphology of the obtained Sr 3 SiO 5 :Eu 3+ powder was examined by SEM (Figure 1c), and the corresponding EDX spectrum confirmed the presence and homogeneous distribution of Sr, Si, and Eu. The PL and PLE spectra for Sr 3 SiO 5 :Eu 3+ prepared in air are given in Figure 2a.…”

“…The relatively high intensity ratio of the Eu 3+ emission transitions for 5 D 0 → 7 F 2 compared to 5 D 0 → 7 F 1 is consistent with the distortion of the [SrO 6 ] octahedra, given that Eu 3+ ions are expected to occupy the Sr 2+ sites. 42,48 For the excitation spectrum, the strong broad band centered at 330 nm is ascribed to the Eu 3+ −O 2charge transfer state, while the weaker lines in the range from 375 to 470 nm correspond to the interconfigurational 4f 6 −4f 6 transitions of Eu 3+ . 49 After illumination with a 254 nm lamp for 50 min, broad bands in the range of 380−550 nm (PLE spectrum) and 510−560 nm (PL spectrum) emerge when recording at the same excitation and emission wavelengths as before (Figure 2a).…”

“…Eu 2+ - or Ce 3+ -doped Cs 3 CoCl 5 -type phosphors have been widely studied in the past 20 years for their application in white LEDs due to their excitation band matching well with the NUV or blue emission of the chips, a high luminescence efficiency, and an especially tunable broad band emission owing to the flexible crystallographic environment of their cations . Among them, Sr 3 SiO 5 :Eu 2+ has drawn extra attention since it was reported to exhibit persistent luminescence, OSL, and so-called zero-thermal quenching behavior, all of which have been related to the electron transfer between Eu and trapping defects (or codopants). − In this work, the phenomena of photo-reduction (Eu 3+ → Eu 2+ ) and the following reverse process of photo-induced or thermally induced oxidation (Eu 2+ → Eu 3+ ) are demonstrated in Sr 3 SiO 5 :Eu 3+ .…”

Up‐conversion phosphor plate for white lighting device using NIR excitation source

“…The thermal quenching (TQ) properties of the Y 2 O 3 :Er 3+ , Yb 3+ and Y 2 O 3 :Tm 3+ , Yb 3+ PiG samples were studied from room temperature to 200ºC, as shown in Figure 4A and B, respectively. Generally, the PL efficiency of the PiG samples decreases for increasing the temperature of the LED due to enhanced nonradiative transition 18‐20 . As the temperature increases, the Y 2 O 3 :Er 3+ , Yb 3+ PiG exhibits a gradually decreasing luminescence.…”

“…Generally, the PL efficiency of the PiG samples decreases for increasing the temperature of the LED due to enhanced nonradiative transition. [18][19][20] As the temperature increases, the Y 2 O 3 :Er 3+ , Yb 3+ PiG exhibits a gradually decreasing luminescence. At 100ºC, the emission intensity of the main peak (λ em = 670 nm) is approximately 65% of that at room temperature, whereas the Y 2 O 3 :Tm 3+ , Yb 3+ PiG retains 80% of the room-temperature peak emission intensity, as shown in Figure 4C.…”