Multiwavelength Excitation in Ho<sup>3+</sup>-Doped All-Inorganic Double Perovskites Achieved by Codoping Mn<sup>2+</sup> for Warm-White LEDs and Plant Growth
Yiying Zhu, Guoxun Sun, Yining Wang, Yixin Sun, Xiaole Xing, Mengmeng Shang
Abstract
Doping lanthanide ions is an efficient method to modify the optical properties of lead-free double-perovskite halides. However, most lanthanide-doped double perovskites show a low luminescence efficiency and require a high excitation energy. Here, we have successfully prepared a series of Ho 3+ -doped Cs 2 NaBiCl 6 microcrystals through a simple hydrothermal method and obtained strong characteristic emissions of Ho 3+ at 492 and 657 nm under low-energy excitation (449 nm). After codoping Mn 2+, apart from the characteristic emissions from Ho 3+ under 450 nm wavelength excitation, the orangish-red luminescence consisting of the emission band centered at 591 nm from Mn 2+ and a sharp emission peak at 657 nm from Ho 3+ is obtained under 355 nm UV light excitation. Photoluminescence (PL) emission and excitation spectra, along with the PL decay curves, confirm the existence of an energy-transfer channel from Cs 2 NaBiCl 6 to Mn 2+ and then from Mn 2+ to Ho 3+ . The enhanced absorption efficiency (10.5 → 70.7%) suggests that the codoping of Mn 2+ overcomes the low absorption efficiency caused by f–f forbidden transitions of Ho 3+ . Finally, the diverse luminescent performance within the Cs 2 NaBiCl 6:Ho 3+, Mn 2+ phosphor is realized by altering the excitation wavelength, thereby enabling its application in warm-white-light-emitting diodes and plant growth in this work.