Cesium iodide (CsI) can be used as a cathode for the fabrication of field emission cathodes for potential usage in high power microwave systems. It can also be used to form an interface layer between the blocking layer and the perovskite active layer to improve the photovoltaic performance and stability of solar cells.

Frequently used in devices such as phosphor screens for medical imaging, scintillators, calorimeters and a variety of particle detectors.