Excitation Dynamics in Layered Lead Halide Perovskite Crystal Slabs and Microcavities

Lead halide perovskites are promising materials for various optoelectronic device applications such as solar cells, light-emitting diodes, and lasers. Three-dimensional perovskites, for example, CH₃NH₃PbI₃ and CsPbBr₃, have been demonstrated to be high-gain active media for low-threshold lasing. In contrast, layered perovskites, for example, (CH₃(CH₂)₃NH₃)₂PbI₄, are known to be difficult to show lasing oscillation especially at room temperature, despite their robustness for the environment. Here we reveal the bottleneck for the lasing oscillation in layered perovskites through systematic experiments on time-resolved photoluminescence and transient absorption. It is found that the energy transfer to a long-lived exciton state with triplet nature is enhanced by increasing pumping fluence or by introducing a high-Q microcavity, hindering the formation of population inversion. These results are consistent with a coupled rate-equation model as well as previous works and paves the way for designing low threshold layered perovskite lasers.