Metal-halide perovskite (MHP) thin films show promise for integration into optoelectronic and spin-based devices. Here, we investigate spin dephasing in vapor-deposited CsPbBr₃ thin films via a combination of time-resolved Faraday rotation and magnetic circular dichroism spectroscopy. We observe coherent precession of both photogenerated electron and hole spins. For photogenerated holes, spin-dephasing times (T₂^*) can be elongated at cryogenic temperatures from 282 to 320 ps by application of a small magnetic field, which partially suppresses hyperfine dephasing.

At elevated temperatures, hole-spin dephasing is accelerated by thermally excited longitudinal-optical phonons, but coherent hole-spin precession is still measurable at room temperature. Photogenerated electrons show rapid spin dephasing (∼40 ps) even at cryogenic temperatures. These results highlight that vapor-deposited CsPbBr₃ thin films offer a compelling platform for harnessing spins in MHP semiconductors, and their scalable manufacturing offers an attractive pathway to future device integration.