| 1. |
- Braun, Cordula, et al.
(författare)
-
Closing the yellow gap with Eu- and Tb-doped GaN : one luminescent host resulting in three colours
- 2022
-
Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 12:1
-
Tidskriftsartikel (refereegranskat)abstract
- Gallium nitride (GaN) is a key material when it comes to light-emitting diodes (LEDs) and has pushed the LED revolution in lighting and displays. The concept of down-conversion of a GaN-based blue LED offers the possibility to provide efficient generation of monochromatic, high-color purity light resulting in a highly efficient warm-white all-nitride phosphor-converted light emitting diode (pc-LED). Although the down conversion of blue light from InGaN LEDs has become a dominant technique for producing white light, there are still some technical challenges, e.g. the immiscibility of GaN and InN and the lattice mismatch between the substrate and InGaN, that have to be overcome. Here we demonstrate the doping of bulk GaN with europium, terbium and the combination of both resulting in intriguing luminescence properties, pushing the role of GaN:Eu,Tb as a chief component in future light emitting diodes. This colour tuning proves that one luminescence host can provide three colours (red, green and orange) and that even the so called “yellow gap” could be closed with a III-nitride. By using one material for all colours, it will be possible to overcome the technical challenges in building up LED devices, which will open up new capabilities for modern highly efficient phosphors.
|
|
| 2. |
- Jaworski, Aleksander, et al.
(författare)
-
14N, 13C, and 119Sn solid-state NMR characterization of tin(II) carbodiimide Sn(NCN)
- 2021
-
Ingår i: Zeitschrift für Naturforschung. B, A journal of chemical sciences. - : Walter de Gruyter GmbH. - 0932-0776 .- 1865-7117. ; 76:10-12, s. 745-750
-
Tidskriftsartikel (refereegranskat)abstract
- We report the first magic-angle spinning (MAS) nuclear magnetic resonance (NMR) study on Sn(NCN). In this compound the spatially elongated (NCN)(2)- ion is assumed to develop two distinct forms: either cyanamide (NEC-N2-) or carbodiimide (N-=C=N-). Our N-14 MAS NMR results reveal that in Sn(NCN) the (NCN)(2-) groups exist exclusively in the form of symmetric carbodiimide ions with two equivalent nitrogen sites, which is in agreement with the X-ray diffraction data. The N-14 quadrupolar coupling constant vertical bar C-Q vertical bar approximate to 1.1 MHz for the N-=C=N- ion in Sn(NCN) is low when compared to those observed in molecular compounds that comprise cyano-type N C- moieties (vertical bar C-Q vertical bar > 3.5 MHz). This together with the information from N-14 and C-13 chemical shifts indicates that solid-state NMR is a powerful tool for providing atomic-level insights into anion species present in these compounds. The experimental NMR results are corroborated by high-level calculations with quantum chemistry methods.
|
|
