Improvement of the Water Resistance of a Narrow‐Band Red‐Emitting SrLiAl3N4:Eu2+ Phosphor Synthesized under High Isostatic Pressure through Coating with an Organosilica Layer. Issue 33 (5th July 2016)

• Record Type: Journal Article
• Authors: Tsai, Yi‐Ting; Nguyen, Hoang‐Duy; Lazarowska, Agata; Mahlik, Sebastian; Grinberg, Marek; Liu, Ru‐Shi
• Is Part Of: Angewandte Chemie international edition. Volume 55:Issue 33(2016)
• Page Start: 9652
• Page End: 9656
• Publication Date: 2016-07-05
• Subjects: charge transfer -- coatings -- light-emitting diodes -- luminescence -- phosphors; Chemistry -- Periodicals; 540
• DOI: 10.1002/anie.201604427
• Languages: English
• ISSNs: 1433-7851

Abstract

Abstract: A SrLiAl3 N4 :Eu 2+ (SLA) red phosphor prepared through a high‐pressure solid‐state reaction was coated with an organosilica layer with a thickness of 400–600 nm to improve its water resistance. The observed 4f 6 5d→4f 7 transition bands are thought to result from the existence of Eu 2+ at two different Sr 2+ sites. Luminescence spectra at 10 K revealed two zero‐phonon lines at 15377 (for Eu(Sr1)) and 15780 cm −1 (for Eu(Sr2)). The phosphor exhibited stable red emission under high pressure up to 312 kbar. The configurational coordinate diagram gave a theoretical explanation for the Eu 2+/3+ result. The coated samples showed excellent moisture resistance while retaining an external quantum efficiency (EQE) of 70 % of their initial EQE after aging for 5 days under harsh conditions. White‐light‐emitting diodes of the SLA red phosphor and a commercial Y3 Al5 O12 :Ce 3+ yellow phosphor on a blue InGaN chip showed high color rendition (CRI=89, R 9=69) and a low correlated color temperature of 2406 K. Abstract : Stay dry and warm in this coat : The red‐emitting phosphor SrLiAl3 N4 :Eu 2+ has superior luminescence properties but is water‐sensitive and generally synthesized from metal‐hydride precursors. These limitations were overcome by the use of a high‐pressure synthetic method and the application of an organosilica coating. The resulting material with enhanced optical properties was used to make high‐performance warm‐white‐light‐emitting diodes.