Synthesis and Stability of Cs ₃ MnBr ₅ : An In-Depth Study on the Effect of Zinc Alloying

Today, the development of green phosphors is becoming a hot topic as they could be combined with blue light-emitting diodes (LEDs) to replace low-efficiency green LEDs. With its intense green emission under blue or UV excitation, Cs₃MnBr₅ appears to be a promising candidate. However, this phase is highly hygroscopic, and partial substitution of Mn with Zn has been proposed to overcome this challenge. In this article, the influence of zinc content on Cs₃Mn_1-<i>x</i>Zn_<i>x</i>Br₅ is investigated in terms of structure, optical properties, and stability under a humid atmosphere. A pure phase is obtained for 0.4 ≤ <i>x</i> ≤ 0.8, and XANES and SQUID studies revealed that manganese remains in its +II state regardless of the zinc content. Zinc increases internal quantum yields but decreases blue-light absorption, and the best compromise giving the highest green emission is obtained for <i>x</i> = 0.5. In situ XRD results shows that the optimized solid solution Cs₃Mn_0.5Zn_0.5Br₅ is not hydrated, even at 100% relative humidity, whereas Cs₃MnBr₅ is fully transformed above 50% RH. More generally, by providing a better understanding of the influence of zinc on the optical properties and moisture stability of Cs₃MnBr₅, this work paves the way for the future development of this phosphor in (micro)-LED applications.