  Lead-halide perovskites are highly promising for various optoelectronic
applications including laser devices. However, fundamental photophysics
describing the lasing behaviour in this material family have not been
investigated systematically, and thus the detailed lasing mechanism remains
veiled. Here, we demonstrate that an all-inorganic perovskite shows a lasing
emission based on a novel principle. A series of photoluminescence experiment
results reveals that the excited state of CsPbBr3 single crystal exhibits free
carrier nature. In a form of microcavity, on the other hand, the CsPbBr3 single
crystal shows emission from polaritonic excited state, demonstrating the
coexistence of excitonic nature. Room temperature polariton lasing is also
clearly observed. This unprecedent mechanism, i.e. polariton lasing based on
free-carrier reservoir, is accomplished by the exciton/free-carrier hybrid
nature of CsPbBr3.
