From Dopant to Host: Solution Synthesis and Light‐Emitting Applications of Organic‐Inorganic Lanthanide‐Based Metal Halides

• Published in: Small structures Vol. 5; no. 7
• Main Authors: Bai, Tianxin, Wang, Qiujie, Bai, Yunfei, Meng, Qichao, Zhao, Hongyuan, Wen, Ziying, Sun, Haibo, Huang, Li, Jiang, Junke, Huang, Dan, Liu, Feng, Yu, William W.
• Format: Journal Article
• Language: English
• Published: Weinheim John Wiley & Sons, Inc 01.07.2024; Wiley; Wiley-VCH
• Subjects: anti‐counterfeiting application; Chemical Sciences; Crystallization; Energy levels; Erbium; Europium; Halides; Holmium; lanthanide LED; lanthanide phosphor; lead‐free metal halides; Light emitting diodes; Metal halides; Near infrared radiation; Optoelectronic devices; Perovskites; Phosphors; Photoluminescence; rare‐earth compounds; Samarium compounds; Terbium; Thulium; Ytterbium; Lanthanide; Optoelectronics; Chemical engineering; Doping; Materials science; Ion; Ecology; Biology; Metal; Halide; Organic chemistry; Engineering; Chemistry; Host (biology); Inorganic chemistry; Dopant; Metallurgy
• ISSN: 2688-4062; 2688-4062
• DOI: 10.1002/sstr.202400096

The rich and unique energy level structure arising from 4fn inner shell configuration of trivalent lanthanide ions (Ln3+) renders them highly attractive for light‐emitting applications. Currently, research primarily focuses on Ln3+ doping in either traditional garnets or the recently developed perovskite phosphors. However, there have been few reports on stable phosphors crystallized with pure lanthanide elements. Herein, a universal solution‐based route to eight Ln3+‐based metal halides from the organic‐inorganic A4LnX7 family is described, where A+ =  4,4‐difluoropiperidinium (DFPD+), Ln3+ =  Nd3+, Eu3+, Ho3+, Sm3+, Tm3+, Tb3+, Yb3+, Er3+, and X− =  Cl−, Br−. Visible photoluminescence (PL) is observed from Tb3+‐, Eu3+‐, Ho3+‐, and Sm3+‐based compounds with Tb and Eu compositions exhibiting high PL quantum yields of 90–100%; Nd3+‐, Tm3+‐, Yb3+‐, and Er3+‐based crystals show fascinating near‐infrared emission. Light‐emitting diodes (LEDs) fabricated with (DFPD)4TbCl7 yield characteristic emission of Tb3+, representing the first demonstration of electroluminescence from these organic‐inorganic Ln3+‐based metal halides. Moreover, these materials exhibit distinct excitation wavelength‐dependent emission after alloying with different Ln3+ ions, making them interesting for multicolor display and multilevel information encryption applications. It is foreseen that this study will open up the way to a possible design of robust optoelectronic devices based on lanthanide metal halides. A versatile method for the solution synthesis of eight organic‐inorganic lanthanide ion‐based metal halides is proposed. The synthesized (4,4‐difluoropiperidinium)4LnX7 compounds (Ln3+ = Nd3+, Eu3+, Ho3+, Sm3+, Tm3+, Tb3+, Yb3+, Er3+, and X− = Cl−, Br−) effectively retain the characteristic emissions of Ln3+ ions, while also exhibit excellent film‐forming ability at low temperature.