Elucidation of lasing mechanism in all-inorganic perovskite microcavity with exciton/free-carrier hybrid nature

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.