Moisture‐Resistant Mn4+‐Doped Core–Shell‐Structured Fluoride Red Phosphor Exhibiting High Luminous Efficacy for Warm White Light‐Emitting Diodes

• Published in: Angewandte Chemie International Edition 2019-03, Vol.58 (12), p.3843-3847
• Main Authors: Huang, Decai, Zhu, Haomiao, Deng, Zhonghua, Zou, Qilin, Lu, Hongyu, Yi, Xiaodong, Guo, Wang, Lu, Canzhong, Chen, Xueyuan
• Format: Article
• Language: English
• Subjects: Aging; cation exchange; Cation exchanging; Color; Color temperature; Commercialization; Core-shell structure; Diodes; Effectiveness; Emission; Fluorides; Luminous efficacy; Mn4; Moisture resistance; Organic light emitting diodes; Phosphors; photoluminescence; Surface defects; White light
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.201813363

K2TiF6:Mn4+ is a highly efficient narrow‐band emission red phosphor with promising applications in white light‐emitting diodes (LEDs) and wide‐gamut displays. Nevertheless, the poor moisture‐resistant properties of this material hinder commercialization. A convenient reverse cation‐exchange strategy is introduced for constructing a core–shell‐structured K2TiF6:Mn4+@K2TiF6 phosphor. The outer K2TiF6 shell acts as a shield for preventing moisture in the air from hydrolyzing the internal MnF62− group, while effectively cutting off the path of energy migration to surface defects, thereby increasing the emission efficiency (especially for the phosphors doped with high concentrations of Mn4+). Employed as a red phosphor, the packaged white LED exhibits an extraordinarily high luminous efficacy of 162 lm W−1, a correlated color temperature (CCT) of 3510 K, and a color rendering index of 93 (Ra). Aging tests performed on this device at 85 °C and 85 % humidity for 480 h retain up to 89 % luminous efficacy. The findings could facilitate commercial application of K2TiF6:Mn4+@K2TiF6 phosphor. A reverse cation‐exchange strategy is presented for the construction of a core–shell‐structured K2TiF6:Mn4+@K2TiF6 (KTF:Mn4+@KTF) phosphor. The KTF shell shields the KTF:Mn4+ core from ambient moisture and prevents hydrolysis of the internal MnF62− group. The phosphor exhibits a high photoluminescence quantum yield and excellent moisture‐resistant properties.