Inorganic cesium manganese halides: Insights into optical properties, coordination chemistry, synthesis methods and optoelectronic applications

In recent years, remarkable progress has been made in research on cesium manganese halides. These materials have sparked intense research interest in applications that require rapid response rates, such as X-ray scintillation and optical communication, due to their high PLQY and tunable radiative lifetimes depending on the shortest Mn-Mn distance. This review aims to provide an in-depth and exclusive review of cesium-Mn metal halides with respect to their optical, electronic, and spectroscopic properties, as well as their coordination chemistry. We explain the ion-luminescence emission mechanism and its dependency on the local coordination around the Mn²⁺ ions. Fundamental principles such as Mn-Mn coupling interactions, Mn-Mn distance, and d–d transition selection rules are discussed in depth. Then, we discuss the three most common protocols for synthesizing Mn halide perovskites. In conclusion, we provide perspectives to establish a clear and comprehensive understanding to optimize the structure-luminescence relationship to pioneer strategies to overcome challenges in cesium-Mn halides and develop optoelectronic devices.