Used as a base and source of caesium in organic synthesis, particularly in coupling reactions such as the Suzuki and Heck reactions. Enhances reactivity in nucleophilic substitutions due to its high solubility in polar solvents. Employed in the preparation of pharmaceuticals, agrochemicals, and fine chemicals. Also utilized in the production of specialty glasses and optical materials for its ability to modify refractive index and thermal stability. Plays a role in catalysis and in the synthesis of perovskites for solar cell applications.