UV polaritons at room temperature in a microcavity containing perovskites

The molecular crystal of ( C 6 H 5 C 2 H 4 – NH 3 ) 2 PbCl 4 perovskite presents an excitonic state with an absorption energy in the ultraviolet range (3.64 eV, 341 nm) and a large binding energy (few hundred of meV). We report here on the realization of a Perot–Fabry λ -microcavity containing a thin film of this material as active layer. Angle-resolved reflectivity and photoluminescence measurements demonstrate this microcavity works, at room temperature, in the strong coupling regime: the cavity photon mode and the excitonic state are not eigenmodes of the system any more, the new eigenmodes are a linear and coherent superposition of the exciton and photon states, called cavity polaritons.