Crystallization of Na<sub>2</sub>SrGe<sub>6</sub>O<sub>14</sub>:Cr<sup>3+</sup>,Yb<sup>3+</sup> Glass Ceramics Enabling a Watt‐Level Output Power NIR‐I/NIR‐II Lighting Source
Taoze Wang, Yuzhen Wang, Weibin Chen, Zhiguo Xia
Abstract
Abstract Near‐infrared (NIR) phosphor‐converted light‐emitting diodes (pc‐LEDs) lighting sources are applied in non‐destructive examination and illumination supplements for night monitoring. As a critical component of NIR pc‐LED, NIR phosphors are required to possess a high external quantum efficiency (EQE), super thermal stability, and broadband emission to meet applications. Here, Na 2 SrGe 6 O 14 :Cr 3+ (NSGO:Cr) glass ceramics (GC) bulk via highly crystallization from glass precursor is fabricated and demonstrates an ultrabroad emission band centered at 815 nm with a full width at half‐maximum (FWHM) of 214 nm and a high EQE of 49.2%. Moreover, Yb 3+ co‐doping significantly enhances Cr 3+ → Yb 3+ energy transfer (ET) due to the stronger Yb 3+ : 2 F 7/2 ‐ 2 F 5/2 absorption. Benefiting from the ET process, the Cr/Yb co‐doped GC exhibits NIR‐I/II emission with improved thermal stability from 30.1% to 65.0%. Furthermore, an encapsulant‐free NIR GC‐converted LED (GCc‐LED) is prepared and exhibits 52.2 mW NIR output power with a high photoelectric conversion efficiency (PCE) of 19.4%. Under a large current of 600 mA, the NIR device exhibits a watt‐level output power of 922.4 mW with a PCE of 9.1%. Compared to conventional NIR powder phosphors, NSGO:Cr/Yb GC with high performance can open up an avenue for the fabrication of high power NIR lighting sources.