Photon Echo Polarimetry of Excitons and Biexcitons in a CH₃NH₃PbI₃ Perovskite Single Crystal

Lead halide perovskites show remarkable performance when used in photovoltaic and optoelectronic devices. However, the peculiarities of light-matter interactions these materials general are far from being fully explored experimentally theoretically. Here we specifically address energy level order optical transitions demonstrate photon echos a methylammonium lead triiodide single crystal, thereby determining coherence times $T_2$ for excitons biexcitons at cryogenic temperature to be 0.79 ps 0.67 ps, respectively. Most importantly, have developed an experimental photon-echo polarimetry method that not only identifies contributions exciton biexciton complexes, but also allows accurate determination binding 2.4 meV, even though period quantum beats between is much longer than resonances. Our theoretical analysis methods contribute understanding complex mechanism quasiparticle moderate pump density high-quality perovskite crystals very low temperatures, inhomogeneous broadening excitonic due local crystal potential fluctuations source dephasing.