The Transition Mechanism and Multifunctional Applications in Vapochromic Organic–Inorganic Mn‐Based Halides

Organic–inorganic metal halides (OIMHs) are highly promising multifunctional optoelectronic materials, owing to their complex and variable characteristics derived from the two distinct components of organic and inorganic parts. However, stability‐related deficiencies limit its performance and the expansion of its application scenarios. Here, to advance the understanding and development of stability in OIMH system, the state transition mechanism of a versatile manganese‐based (Mn) OIMH with both steady and non‐steady states is investigated. By low temperature annealing (60 °C), the OIMH exhibits non‐steady property and becomes sensitive to the moisture, showing reversible thermochromic photoluminescence in ambient atmosphere. While being subjected to a higher annealing temperature (110 °C), the OIMH becomes quite steady and shows an irreversible, strong green emission with significantly improved PLQY (from 38% to 99%) and high stability (18 months) in ambient atmosphere. Through experiments and density functional theory (DFT) simulations, the microscopic dynamic mechanism of the reversible vapochromic phenomenon and the irreversible monochromatic emission phenomenon is thoroughly revealed. Understanding the microscopic structural transmission mechanism of vapochromism in Mn‐based materials is crucial for developing corresponding research strategies for high‐performance applications. This is also highly significant for advancing the stability and performance of novel optoelectronic materials in OIMH systems.