The Renascence of One Ancient Recipe for Synthesizing Luminescent Cs₄PbBr₆ Microcrystals

One ancient recipe to produce rocky candies has found new applications in synthesizing Cs₄PbBr₆ microcrystals, one 0D perovskite with [PbBr₆]⁴⁻ octahedra isolated by Cs⁺ bridges that enable quantum confinement and high exciton binding energy favorable for photoluminescence (PL). Herein, various threads are used as seeds to grow perovskites microcrystals, in a way similar to rocky candy production recorded in ancient Chinese recipes. The Cs₄PbBr₆ growth is an exothermic enthalpy driving process, with the surface energy differentiation determining the formation of rhombohedra shape. The synthesized Cs₄PbBr₆ microcrystals show a large PL quantum yield (PLQY) of 31.5% and are used to fabricate white and green light-emitting diodes with high performance. Learning from history, this work provides one controllable and generally applicable avenue of fabricating high-quality perovskite crystals with promising applications in photonic and optoelectronic devices, and the elucidation of the growth mechanism offers useful guidance for critical factors directing crystal fabrications in future work.